If the legs of a right triangle are 3 feet and 4 feet the length of the hypotenuse is

Use the Pythagorean theorem to solve this.

The Pythagorean theorem says that:
If a and b are the legs of a right triangle, and c is the hypotenuse, then

a^2+b^2=c^2.

Substiute in the values that you know to the equation.

3^2+4^2=c^2
9+16=c^2
25=c^2
5=c

The length of the hypotenuse is 5 feet.

Hope this helps!