the answer would be 4
if you look at the third part of the original equation, you can see that it is subtracting 8x^5
since there is no x^5 in the simplified form, you can assume it was canceled out by a positive 8x^5
if you divide 8x^5 by 2x^2 (which is in the second section of the original equation) you get 4x^3 which tells you that m needs to be 4