The perimeter is the total of adding all of the side lengths together.
s = shortest side
L = longest side
T = third side
L = s + 6 (longest side is 6 more units than the shortest side)
T = 2s (the third side is twice the length of the shortest side)
Equation is:
P = s + L + T
You can plug in the equations of L = s + 6 and T = 2s into "L" and "T":
P = s + L + T
P = s + (s + 6) + (2s) You know the perimeter is 26, so you can plug it into P
26 = s + s + 6 + 2s
26 = 2s + 6 + 2s
26 = 4s + 6
20 = 4s
5 = s
Now that you know s, you can plug it into L = s + 6 and T = 2s
L = s + 6
L = 5 + 6
L = 11
T = 2s
T = 2(5)
T = 10
The shortest side is 5 units, the longest side is 11 units, the third side is 10 units