Answer:
<h2>x = 7 cm</h2>
Step-by-step explanation:
The perimeter of the given triangle:
P = (2x + 1) + (x + 2) + (3x - 9) and P = 36 cm.
Therefore we have the equation:
2x + 1 + x + 2 + 3x - 9 = 36 <em>combine like terms</em>
(2x + x + 3x) + (1 + 2 - 9) = 36
6x - 6 = 36 <em>add 6 to both sides</em>
6x = 42 <em>divide both sides by 6</em>
x = 7
