If x=5 what is the perimeter of the rectangle whose length is 6x-4 and 3x+2

If x=5, substitute 5 into all the x that appears in the equation.

perimeter of the rectangle
= 2(length) + 2(breadth)
= 2 (6x-4) + 2(3x+2)
= 12x - 8 + 6x + 4

now substituting in x=5,
perimeter
= 12(5) - 8 + 6(5) + 4
= 60 - 8 + 30 + 4
= 86