Ok, so,
the equation is ($x ÷ 2) + $5 = $13, and (one way) to figure out x, is to do the equation backwards.
So we need to subtract $13 by $5.
$13 – $5 = $8
Then we take that $8 and multiply it by 2.
$8 × 2 = $16.
So, his weekly allowance is $16.
And, to double check.....
($16 ÷ 2) + $5 = $13
I hope this helped!
Have a great day! : )