step 1: open brackets n rmb to flip the signs
step 2 (optional): rearrange to make the equation clearer to add/minus
length of 3rd side:
(8x + 3) - (2x + 1) -(5x + 2)
= 8x + 3 - 2x -1 - 5x -2
= 8x -2x -5x +3 -1 -2
= x
Therefore, length of 3rd side is X cm.
---
If perimeter = 75cm,
8x +3 = 75
8x = 75-3
8x = 72
x = 9 cm
Therefore,
1st side = 2(9) +1
= 19 cm
2nd side = 5(9) +2
= 47 cm
3rd side = 9 cm
