if coefficient of x^-7 and x^-8 to the expansion of (2+1/3x)^n are equal then n=?

if coefficient of x^-7 and x^-8 to the expansion of (2+1/3x)^n are equal then n=? If the coefficients of and to the expansion of are equal then n — (a) 56 (c) 45 55 • In theexpansion of(l + X)' the coefficient

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