Question

n!/(n-4)!+ n!/(n-3)! = 10.n!/(n-3)​!

Answer 1

n!/(n-4)!+ n!/(n-3)! = 10.n!/(n-3)!

n!/(n-4)!+ n!/(n-3)(n-4)! =10.n!/(n-3)(n-4)!

1 + 1/(n-3) = 10/(n-3)

9/(n-3) = 1

n-3=9

n=12