C^2+7 would equal 88. the first equation states that C=9, so you can just plug in 9 for C
we have to find equation similar to

Firstly , we can divide both sides by 2


now, we can multiply both sides by 3

we get
............Answer
You would start out by putting 225 over 100 then simplifying from there. You would end up getting 9/4. As a mixed number that would be 2 and 1/4.
Large cab doors= 12.5x2.5= 31.25in
1feet = 12in
12feet X 12 = 144in board
144 / 31.25 = 4.608
4 large doors can be cut
19in left over