Answer:
13x + 112 = 320.
Step-by-step explanation:
The perimeter is the sum of the 3 sides:
1/2 x + 3/8 x + 11 + 3/4 x + 3 = 40
1/2 x + 3/8 x + 3/4 x + 3 + 11 = 40
1/2 x + 3/8 x + 3/4 x + 14 = 40
Multiply through by 8 to remove the fractions:
4x + 3x + 6x + 14 = 40
13x + 112 = 320.
