You need to write a^2 + b^2 = c^2 and fill in what you know
12^2+x2=(8+x)2 Simplify both side
x^2+144=x^2+16x+64 Subtract x^2 from both sides.
x^2+144−x^2=x^2+16x+64−x^2144=16x+64 Subtract 64 from both sides.
16x+64−64=144−64
16x=80 Divide both sides by 16.
16x/16=80/16
x=5
