The measure of two side of a triangle are given if p is the perimeter and p=18x+9y find the measure of the third side

Answer:
10x + 6y
Step-by-step explanation:
Let t = length of the third side
3x + 4y + 5x - y + t = 18x + 9y
8x + 3y + t = 18x + 9y
t = 10x + 6y