find coefficient of x^6y^3 in the expansion of (x+2y)^9

General term in binomial expansion is given by (a + b)ⁿ = ⁿC_r(a)^n-r(b)^r

So a = x and y = 2y and n = 9
So (x +2y )⁹ has general term as  ⁹C_r (x)^9-r (2y)^r
As 9-r = 6
So r = 3
Hence we have coefficient of  ⁹C₃ (x)⁶ 2³y³  = ⁹C₃ *2³