10 m
Step-by-step explanation:
Data:
Second side : x
Third side : four times the second side : 4*x
The other side : 5 m longer than the second side : 5 + x
Perimeter of the triangle : 65 m
Formula:
Perimeter of a triangle = one side + second side + third side
Solution:
65 = 5 + x + x + 4 * x
65 = 5 + 6 * x
65 - 5 = 5 + 6 * x - 5
60 = 6 * x
60 / 6 = 6 * x / 6
10 = x