If 3 x+7 y=75 and 5 x-5 y=25, then what is the value of x+y ? · ABC26GN1047

$$\begin{aligned} & 3 x+7 y=75 \\ & 5 x-5 y=25 \Rightarrow x-y=5 \Rightarrow 7 x-7 y=35 \end{aligned}$$ Adding (i) and (ii), we get: $10 x=110$ or $x=11$. Putting $x=11$ in (i), we get: $7 y=42$ or $y=6$. $$\therefore \quad x+y=(11+6)=17 .$$