Rewrite without parentheses and simplify. \[ (5 u+6 y)^{2} \]

3. \( 55 m^{2} n^{3} x+110 m^{2} n^{3} x-220 m^{2} y^{3} \)

solving the following system \[ \left\{\begin{array}{l}x+y=51 \\ 5 x+10 y=425\end{array}\right. \]

Which expression is equivalent to \( \left(3 x^{2} y\right)^{2}\left(2 x^{4} y^{2}\right)^{2} \) ? A \( 10 x^{10} y^{6} \) B \( 12 x^{24} y^{8} \) C \( 24 x^{10} y^{7} \) D \( 36 x^{12} y^{6} \)

Simplify \( \frac{16 x^{4}}{4 x^{4}} \) \( \begin{array}{ll}\text { A } & 4 \\ \text { B } & 12 \\ \text { C } & 4 x \\ \text { D } & 12 x\end{array} \)

2. \( 15 m^{2} n+30 m n \)