Use the pythagorean theorem which works for right triangles. Its a squared + b squared=c squared. c is 13 since that's the length of the side opposite of the right angle so its the hypotenuse which is c. 5 is a leg. Plug them in. (5) squared + bsquared=(13) squared Simplify. 25+bsquared=169 subtract 25 from both sides b squared equals 144 find square root of both sides b=12
