Answer:
Marina's design uses more cardboard.
in Kristen's design, it uses:
3*4/2*2+10*5+3*10+4*10=132 sq inches.
in Marina's design, it uses:
6*3*2+3*7*2+7*6*2=162 sq inches.
132<162
Therefore Marina's design uses more cardboard.
The difference between 2 designs are:
162-132
=30 sq inches
