Answer:
20 inches x 26 inches
Step-by-step explanation:
set up an equation: (2x)(x+7)=520
now just solve it
2x^2+14x=520
x^2+7x-260 = 0
factor: (x-13)(x+20)
x = 13 and -20
13 is the only one that works because you can't have a negative side length
13+7=20
13*2=26
lmk if you don't understand how to solve that equation
