Question

a triangle has side lengths of (7r - 10) centimeters, (5r + 5) centimeters, and (s + 8) centimeters. which expression represents the perimeter, in centimeters, of the triangle?
answer
3 + s + 12r
7r + 9s
-5 + 12r + 9s
9s + 10 - 3r

Explanation:

Step1: Recall perimeter formula

The perimeter $P$ of a triangle is the sum of the lengths of its sides. So $P=(7r - 10)+(5r + 5)+(s + 8)$.

Step2: Remove parentheses

$P = 7r-10 + 5r+5 + s + 8$.

Step3: Combine like - terms

Combine the $r$ - terms: $7r+5r = 12r$. Combine the constant terms: $-10 + 5+8=3$.
So $P=3 + s+12r$.

Answer:

A. $3 + s + 12r$