The leg of a right triangle is 3 units and the hypotenuse is 7 units. What is the length, in units, of the other leg of the triangle

The hypotenuse is a^2 + b^2 = c^2 so lets work in reverse

7^2 - 3^2 = b^2

49-9 = b^2

40 = b^2

since 40 has no square root the other leg is sqrt40 (sorry im on mobile no sqare root sign but you get the gist i hope)