How many solutions are there to the equation x1 + x2 + x3 + x4 + x5 = 21?

where xi , i = 1, 2, 3, 4, 5, is a nonnegative integer such
that 0 ≤ x1 ≤ 10?

I took C(25,4) and subtracted C(10,3) to get 1530. Is this correct?
1 answer 1