~7.62.
Using the Pythagorean Theorem, a^2 + b^2 = c^2, we find the legs of the triangle. Going down, we have 7 units. Going to the right, we have three units.
7^2 + 3^2 = 49 + 9 = 58
Now, we have to square root 58 since we squared the summation of 7^2 and 3^2.
(sqrt 58) ~ 7.62