Question

Can anyone tell me what the midpoint of PQ is?

Answer 1

The formula of the midpoint of PQ:
$\left(\dfrac{x_P+x_Q}{2};\ \dfrac{y_P+y_Q}{2}\right)$

We have P(0; 0) and Q(2a; 0). Substitute:
$\left(\dfrac{0+2a}{2};\ \dfrac{0+0}{2}\right)=(a;\ 0)$