M=(5- 1) ^n=4^n

The sum of binomial coefficients is n = 2 n

m-n=4^n-2 ^n=240=2^n *(2^n- 1)= 16 * 15

n=4

The x term in the expansion is c (4 4,2) * (5x)2 * (1/root x) 2.

=6 *25x^2 * 1/x

= 150x

So the coefficient of the x term is 150.

I hope I can help you and adopt it.