Samuel found the difference of the polynomials. \( \left(15 x^{2}+11 y^{2}+8 x\right)-\left(7 x^{2}+5 y^{2}+2 x\right)=\square x^{2}+6 y^{2} \) What value is missing from his solution?

e) \( (3 x+2) \cdot\left(x^{3}-2 x^{2}+1\right)= \)

5) \( 4(2-x)=x+3 \)

6) \( \frac{1}{x-2}=2 \)

a) \( \log _{2} x=1-x \);

Question 3 A store is selling a large selection of men's shirts, and every shirt has the same price. Kiyoshi buys 6 shirts and gets a \( \$ 30 \) discount. His friend Gregory buys 4 shirts and does not receive a discount. Gregory spends \( \$ 20 \) less than Kiyoshi. What is the price of one shirt without any discount? \( \$ 25 \) \$ \( \$ 5 \) \$ \( \$ 100 \) \( \$ 80 \)