Answer
i) \( X = \frac{25}{14}, Y = \frac{15}{7} \)
ii) \( X = \frac{15}{11}, Y = -\frac{16}{11} \)
iii) \( X = \frac{29}{6}, Y = \frac{13}{6} \)
iv) \( X = \frac{1}{2}, Y = 2 \)
v) \( X = \frac{13}{4}, Y = \frac{1}{8} \)
vii) \( Y = \frac{95}{104} \)
viii) \( X = -\frac{5}{8}, Y = \frac{23}{8} \)
Solution
i)
We have
\[
2X+3Y=10 \quad (1)
\]
\[
4X-Y=5 \quad (2)
\]
Solve (2) for \(Y\):
\[
4X - Y = 5 \implies Y = 4X - 5.
\]
Substitute into (1):
\[
2X + 3(4X-5) = 10.
\]
\[
2X + 12X - 15 = 10 \implies 14X = 25.
\]
\[
X = \frac{25}{14}.
\]
Then,
\[
Y = 4\left(\frac{25}{14}\right) - 5 = \frac{100}{14} - 5 = \frac{50}{7} - 5 = \frac{50-35}{7} = \frac{15}{7}.
\]
---
ii)
The system is
\[
3X-2Y=7 \quad (1)
\]
\[
5X+4Y=1 \quad (2)
\]
Multiply (1) by 2:
\[
6X - 4Y = 14.
\]
Now add (2):
\[
(6X-4Y)+(5X+4Y) = 14+1 \implies 11X = 15.
\]
\[
X=\frac{15}{11}.
\]
Substitute \(X\) into (1):
\[
3\left(\frac{15}{11}\right) - 2Y = 7 \implies \frac{45}{11} - 2Y = 7.
\]
\[
-2Y = 7 - \frac{45}{11} = \frac{77-45}{11} = \frac{32}{11}.
\]
\[
Y = -\frac{16}{11}.
\]
---
iii)
The system is
\[
X+Y=7 \quad (1)
\]
\[
2X-4Y=1 \quad (2)
\]
From (1):
\[
X=7-Y.
\]
Substitute into (2):
\[
2(7-Y)-4Y=1 \implies 14-2Y-4Y=1.
\]
\[
14-6Y=1 \implies -6Y=-13.
\]
\[
Y=\frac{13}{6}.
\]
Then,
\[
X=7-\frac{13}{6}=\frac{42-13}{6}=\frac{29}{6}.
\]
---
iv)
The system is
\[
4X+5Y=12 \quad (1)
\]
\[
2X-3Y=-5 \quad (2)
\]
Multiply (2) by 2:
\[
4X-6Y=-10.
\]
Subtract this from (1):
\[
(4X+5Y)-(4X-6Y)=12-(-10) \implies 11Y=22.
\]
\[
Y=2.
\]
Substitute into (1):
\[
4X+5(2)=12 \implies 4X=12-10=2.
\]
\[
X=\frac{1}{2}.
\]
---
v)
The system is
\[
3X+2Y=10 \quad (1)
\]
\[
2X-4Y=6 \quad (2)
\]
Multiply (1) by 2:
\[
6X+4Y=20.
\]
Now add (2):
\[
(6X+4Y)+(2X-4Y)=20+6 \implies 8X=26.
\]
\[
X=\frac{26}{8}=\frac{13}{4}.
\]
Substitute into (1):
\[
3\left(\frac{13}{4}\right)+2Y=10 \implies \frac{39}{4}+2Y=10.
\]
\[
2Y=10-\frac{39}{4}=\frac{40-39}{4}=\frac{1}{4}.
\]
\[
Y=\frac{1}{8}.
\]
---
vii)
The equation is
\[
2\frac{5}{8}+2\frac{3}{5}Y=5.
\]
Convert the mixed numbers:
\[
2\frac{5}{8}=\frac{21}{8}, \quad 2\frac{3}{5}=\frac{13}{5}.
\]
Thus, the equation becomes
\[
\frac{21}{8}+\frac{13}{5}Y=5.
\]
Isolate \(Y\):
\[
\frac{13}{5}Y=5-\frac{21}{8}=\frac{40}{8}-\frac{21}{8}=\frac{19}{8}.
\]
\[
Y=\frac{19}{8}\cdot\frac{5}{13}=\frac{95}{104}.
\]
---
vi)
The system is
\[
10X+2Y=6 \quad (1)
\]
\[
2X+2\frac{3}{7}Y=6 \quad (2)
\]
Convert the mixed number in (2):
\[
2\frac{3}{7}=\frac{17}{7}.
\]
So (2) becomes
\[
2X+\frac{17}{7}Y=6.
\]
Solve (2) for \(X\):
\[
2X=6-\frac{17}{7}Y \implies X=3-\frac{17}{14}Y.
\]
Substitute into (1):
\[
10\left(3-\frac{17}{14}Y\right)+2Y=6.
\]
\[
30-\frac{170}{14}Y+2Y=6.
\]
Write \(2Y\) as \(\frac{28}{14}Y\):
\[
30-\frac{170-28}{14}Y=6 \implies 30-\frac{142}{14}Y=6.
\]
\[
30-\frac{71}{7}Y=6.
\]
Subtract 30:
\[
-\frac{71}{7}Y=6-30=-24.
\]
\[
Y=24\cdot\frac{7}{71}=\frac{168}{71}.
\]
Then,
\[
X=3-\frac{17}{14}\left(\frac{168}{71}\right).
\]
Simplify:
\[
\frac{168}{14}=12, \text{ so } X=3-\frac{17\cdot 12}{71}=3-\frac{204}{71}.
\]
Write 3 as \(\frac{213}{71}\):
\[
X=\frac{213-204}{71}=\frac{9}{71}.
\]
---
viii)
The system is
\[
X+3Y=8 \quad (1)
\]
\[
7X+5Y=10 \quad (2)
\]
Solve (1) for \(X\):
\[
X=8-3Y.
\]
Substitute into (2):
\[
7(8-3Y)+5Y=10.
\]
\[
56-21Y+5Y=10 \implies 56-16Y=10.
\]
\[
-16Y=10-56=-46.
\]
\[
Y=\frac{46}{16}=\frac{23}{8}.
\]
Then,
\[
X=8-3\left(\frac{23}{8}\right)=8-\frac{69}{8}=\frac{64-69}{8}=-\frac{5}{8}.
\]
---
Final Answers:
i) \(\left(\frac{25}{14},\frac{15}{7}\right)\)
ii) \(\left(\frac{15}{11},-\frac{16}{11}\right)\)
iii) \(\left(\frac{29}{6},\frac{13}{6}\right)\)
iv) \(\left(\frac{1}{2},2\right)\)
v) \(\left(\frac{13}{4},\frac{1}{8}\right)\)
vii) \(Y=\frac{95}{104}\)
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