Find number of whole number solutions of a + b + c + d = 20 where a, b, c and d ≤ 8
= 23c3 - 4 * 14c3 + 4c2 * 5c3
= 1771 - 1456 + 60
why 60 is as added here, if we go by the common way for odthis instead of coefficient method:
so total ways= 23C3- 4*14c3.=315
which 60 cases need to be added here?
Could anyone expalin the part?