C(m,n)=m!/[(m-n)!n!]
C(8,3)=8!/(5!3!)
C(10,3)=10!/(7!3!)
C(8,3)/C(10,3)=[8!/(5!3!)]/[10!/(7!3!)]=(8!7!3!)/(10!5!3!)=(7×6)/(10×9)=7/15