Sonny is twice as old as Wale. Four years ago, he was four times as old as Wale. When will the sum of their ages be 66 ?

\( \begin{array}{l}\qquad x=8 \\ \text { So, length of the given rectangle }=(8+9) \mathrm{cm}=17 \mathrm{~cm} \\ \text { And, breadt of the given rectangle }=8 \mathrm{~cm} .\end{array} \) EXERCISE 15 B 1. 17 less than four times a number is 11 . Find the number.

a) \( \frac{2}{7} x+\frac{5 x}{7}-3 x=8 \)

लगाजनुहोस्ट । If \( \left[\begin{array}{cc}8 & -2 \\ 1 & 4\end{array}\right] A=2\left[\begin{array}{l}6 \\ 5\end{array}\right] \) then find matrix \( A \).

3. Factorize os seguintes polinómios: a) \( 2 x+a x+4 y+2 a y \) b) \( x^{3}-4 x \) \( \begin{array}{l}\text { 4. Sobre a equação do } 2^{\circ} \text { grau, determine a solução da seguinte eq } \\ \left.-2 x^{2}+3 x+5=0-1\right) \\ \text { 5. Encontre a solução do seguinte sistema de } 2 \text { equações: } \\ \qquad\left\{\begin{array}{c}2 x+4 y=11 \\ 5 x-15 y=-20\end{array}\right.\end{array} \)

15. Determine whether the function \( f: \mathbf{Z} \times \mathbf{Z} \rightarrow \mathbf{Z} \) is onto if a) \( f(m, n)=m+n \). b) \( f(m, n)=m^{2}+n^{2} \). c) \( f(m, n)=m \). d) \( f(m, n)=|n| \). e) \( f(m, n)=m-n \).