And I dont know where to start?? For the basis do I take n as being 0, if so r must = 0, there for the basis says n C r = 0 C r = 1.

But what shall the inductive step consist of? If I take (n+1) C r will this work, because r isnt changing in this step so will it be a propor proof???

Please anybody help I am a bit'stuck.

Thanks.

Assume you proved the formula for all n less than N and all r not greater than n. In other words, assume you know nCr as long as n < N. Now prove the formula for n = N and all r <= N.