Hi there the question states 2CR=25 I am really new to this so any help would be appreciated it states to solve for R.
I tried to solve but got no where what i tried was to expand with the formula of nCr and no luck
Using the notation $\displaystyle _NC_k$ unless you are in an advanced mathematics class it is necessary that $\displaystyle N\ge k.$
If that is true then $\displaystyle _NC_k=M$ implies $\displaystyle \frac{N!}{k!(N-k)!}=M$.
Example: $\displaystyle _{N}C_2=105$ implies $\displaystyle \frac{N(N-1)}{2}=105$, solve for N.