The polygon is regular if each of its side has the same length. find the perimeter of the regular polygon. 18, 19, 20

helpp

18. 5-2x = -4x+9
2x = 4
x = 2
perimeter = length of one side x 3
perimeter = [5-2(2)] x 3
= 3

19. 3(x-1) = 5x-6
3x-3 = 5x-6
-2x = -3
x = 1.5
perimeter = [3(1.5-1)] x 5
=7.5

20. 4/3x-⅓ = x+7
4x-1 = 3x+21 (multiply throughout by 3 to get rid of denominator on LHS)
x = 22
perimeter = (22+7) x 6
= 29 x 6
= 174
^ not sure about qn20 because i can’t tell if it’s x+7 or x divided by 7 it’s kinda blurry