Answer:
The equation is p=34a+12, and a=7
Step-by-step explanation:
Perimeter is all of the sides added together
p=12a+6a+8+6a+8+10a-4
Combine like-terms
p=34a+12
Solve for a by making p equal to 250
250=34a+12
Subtract 12 from both sides
238=34a
Divide both sides by 34
7=a