Question

Given, I = a+(n-1) d, express n in terms of I,a and d.

Answer 1

I = a + (n-1)d
I = a + nd - d
nd = I - a + d
n = (I - a + d)/d

Answer 2

l=a+(n-1)d
l=a+dn-d
dn=l-a+d
n=l-a+d/d