Answer:
75 is the length of the third side
The unknown side to the triangle is 75 cm.
Step-by-step explanation
Let x be the length of the unknown side:
x^2 + 40^2 = 85^2
x^2 + 1600 = 7225
x^2 = 7225 - 1600
x^2 = 5625
x = 75
