Kemiringan tangga tsb adalah?

AC^2 = AB^2 + BC^2..(Phitagoras )
AB^2 = AC^2 – BC^2
AB^2 = 15^2 – 12^2
AB^2 = 225 – 144
AB^2 = 81
AB = V81
AB = 9
kemiringan = BC/AB
= 12/9
= 4/3