Question

Surya thought of a number, added 15 to it, then divided the sum by 2 and got 10 as his answer. The number Surya thought of was _________.

Answer 1

Let the number Surya thought of = $x$.
So the equation from the given statement = $\frac{(x+15)}{2}=10$
$\Rightarrow (x+15)=10\times 2$
$\Rightarrow (x+15)=20$
$\Rightarrow x=20-15$
$\Rightarrow x=5$
So the number that he thought of was 5.