Okay, so first you need to understand/recall that the expression can be simplified by distributing the -1 into the parentheses:
[tex] (2m+7)-(3-4m)\\\\(2m+7)+(-1)(3-4m)\\\\2m+7+(-1*3)+(-1*-4m)\\\\2m+7-3+4m\\\\(2m+4m)+(7-3)\\\\6m+4\ is\ your\ answer.[/tex]
