Final answer:
The expression for the perimeter of the triangle is 6x + 5.
Step-by-step explanation:
The expression for the perimeter of a triangle is the sum of the lengths of its three sides.
Perimeter = (3x - 2) + (-5x) + (8x + 7)
Simplify the expression: Perimeter = 3x - 2 - 5x + 8x + 7
Combine like terms: Perimeter = 6x + 5
So, the expression for the perimeter of the triangle is 6x + 5.