Answer:
x= 19
Step-by-step explanation:
First, divide the perimeter by the number of sides;
78/6 = 13
This means that the measurement of each side = 13 units
Given the equation for each side as x-6, equate that to 13 to solve for x;
x-6=13
Add 6 on both sides to become ; x=13+6
Therefore x= 19