Answer:
$9 and $12
Step-by-step explanation:
Let "s" be small boxes and "L" be large boxes.
12*s + 6*L = $180
3*s + 2*L = $51
From the first equation:
L = ($180 - 12*s) / 6 = $30 - 2*s
Plug that into 2nd equation:
3*s + 2*($30 - 2*s) = 3*s + $60 - 4*s = $51
s = $9
L = $30 - 2*s = $30 - $18
L = $12
