How do I do this? You are building a corner cabinet, the walls intersect at a right angle. What is the perimeter of the cabinet if the height is 30 inches, the hypotneuse is 42 inches, and the base is unknown?

Use the Pythagorean Theorem:

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

So it would be like this:

30^2+b^2=42^2

with b representing the unknown value of the base.

900+b^2=1764
b^2=864
b=about 29.4

Add up the sides:

29.4+30+42=?

And that's your answer!