$\begin{aligned}
S(x)= & (1+x)+2(1+x)^2+3(1+x)^3+. .+60(1+x)^{60} \
(1+x) S= & (1+x)^2+\ldots \ldots . \quad 59(1+x)^{60}+60(1+x)^{61} \
& -x S=\frac{(1+x)(1+x)^{60}-1}{x}-60(1+x)^{61}
\end{aligned}$
Put x=60 −60 S=6061((61)60−1)−60(61)61 on solving 3660