Not exactly sure if I’m understanding the question correctly, but here is my answer:
2x+20
Explanation:
I took the equation of the larger rectangle (5x+18) and subtracted the equation of the smaller rectangle (3x-2) from it.
(5x+18) - (3x-2)
Distribute the (-) to the second equation to get 5x+18 -3x+2
Combine alike terms to leave you with 2x+20
