Answer:
other leg = 28 mm
Explanation:
hypotenuse^2 = one leg ^2 + other leg^2
53^2 = 45^2 + other leg^2
subtract 45^2 from both sides to isolate other leg^2
53^2-45^2 = other leg^2 = 784 mm^2
square root both sides to isolate other leg
other leg = 28 mm