Leonard is going to construct a pyramid with cardboard for math class. Find how many square inches (in.^2) of cardboard he will need. Use 4(1/2)bh+b^2, where b, the base of the pyramid, is 3 in. and h, the height of the pyramid, is 8 in.

First, let's find the value of "(1/2)bh":

(1/2)bh = (1/2)(3)(8) = 12 square inches

Then, let's find the value of "b^2":
b^2 = 3^2 = 9 square inches

Finally, let's substitute these values into the formula "4(1/2)bh+b^2":
4(1/2)bh+b^2 = 4(12) + 9 = 48 + 9 = 57 square inches

Therefore, Leonard will need 57 square inches of cardboard.