PLS PLS PLS HELP ME WITH THIS QUESTION!!!!!!!

Answer:
f. 260 in by 100 in
Step-by-step explanation:
13 + 5 = 18
720/18 = 40
Find length:
40*13 = 520
520/2 = 260 <-- must divide by 2, 520 is the sum of twice the length
Find width:
40*5 = 200
200/2 = 100 <-- must divide by 2, 200 is the sum of twice the width