a and b are ALWAYS the legs of the triangle. c is ALWAYS the hypotenuse. Since you're finding c, the shadow's length, then we leave that as c instead of plugging in a number.
Next, find the square of 30 and 42, to leave the equation: 900 + 1,764 = x^2 add 900 + 1,764 to make 2,664.
2,664 = x^2 is what we're left with.
All you need to do now is square root 2,664 to find x instead of x^2
