Answer: About 8.4 mm
Explanation:
Since this is a right triangle, we will solve using the Pythagorean theorem. In the equation we are solving for c, the hypotenuse, with 3.7 mm and 7.5 mm being a and b, the legs.
a² + b² = c²
(3.7)² + (7.5)² = c²
13.69 + 56.25 = c²
69.94 = c²
= c
8.363 mm ≈ c
c ≈ 8.4 mm, when rounded to the nearth tenth of a millimeter
The missing side length is about 8.4 mm.