Squares are cut from the corner, so we are left with only one variable.
The area of a rectangle, the bottom of the pan, is base*height.
Let's call the sides of the removed squares "x"
so 192 = (20-x)(24-x) foil to expand the binomials
192 = 480 - 44x - x squared Take 192 away from both sides
0 = 288 - 44x - x squared
0 = (36 - x)(8-x)
x = 36 and x = 8
Because 36 > 24 and 36 > 20, in this case, the squares cannot be
36cm x 36cm and therefore must be 8cm x 8cm.
Check:
(20-8)(24-8) = 192