Question

I don't know the answer can someone pls help me

Answer 1

line QP =

11.5*(11.5 +24) = 11.5 * 35.5 = 408.25

SqRT(408.25) = 20.205

round answer to 20 units

Answer 2

The formula for your situation is this:
$n^{2} =PN(PN+MN)$
where your PQ is $n^{2}$
So our formula, filled in and solving for PQ is this:
$n^{2}=11.5(11.5+24)$
and $n^{2} =11.5(35.5)$
and n = 20.2 or 20 rounded.  That's the last choice above