Since this is a right triangle, we can you the pythagorean theorem.
a^2 + b^2 = c^2
In this case,
a = 6
b = ?
c = 10
We need to substitute our values into the pythagorean theorem.
(6)^2 + b^2 = (10)^2. Reduce everything to its simplest form.
36 + b^2 = 100. Subtract 36 from both sides.
b^2 = 64. Take the square root of each side.
b = 8.