Find x, if the perimeter is 106
3x+6
2x-3

So we are given that the perimeter is 106 and two problems to solve
we will write this as an equation
106 = 3x + 6
we will subtract 6 from both sides
100 = 3x 
now divide by 3 to isolate the variable
we will get 33 1/3 as the x

for the second one
106 = 2x - 3
add three to both sides
109 = 2x 
divide by 2 to isolate the variable
we will get 54 1/2 as the x

Hope this helps :)