Freddie,
I drew a diagram and labeled some lengths.
From the diagram
x + 2 y = 48
The triangle in the upper right that is to be cut off is a right triangle and hence from Pythagoras theorem
y^{2} + y^{2} = x^{2}
Thus 2 y^{2} = x^{2} and √2 y = x. Substituting into the first equation gives
√2 y + 2 y = 48 so y = ^{48}/_{(√2 + 2)} = 14.06 inches or 14 ^{1}/_{16} inches.
Penny
