The perimeter of a scalene triangle is 14.5 cm. the longest side is twice that of the shortest side. which equation can be used to find the side lengths if the longest side measures 6.2 cm?

The answer is:
a = c ÷ 2
b = P - a - c

The perimeter is the sum of all sides of a polygon. The perimeter of the triangle is:
P = a + b + c
where
P - perimeter of the triangle,
a, b, c - sides of the triangle.

It is given: 
P = 14.5 cm
c = 6.2 cm

If, the longest side (c) is twice that of the shortest side (a), then
c = 2a
Therefore, the equation that can be used to find the length of the shortest side is a = c ÷ 2.

⇒ a = c ÷ 2 = 6.2 cm ÷ 2
⇒ a = 3.1 cm

By knowing two sides (c and a) and perimeter (P), we can calculate the length of the third side (b).
If P = a + b + c, then the equation that can be used to find the length of the side b is b = P - a - c.

⇒ b = P - a - c = 14.5 cm - 6.2 cm - 3.1 cm
⇒ b = 5.2 cm