-7-2(8m+6)=-6m+31

-7-2(8m+6) = -6m+31     simplify the left side

-7 - 16m - 12   =   -6m + 31

-19 - 16m  =  - 6m  +  31      add 6m, 19 to both sides

-10 m   =  50        divide both sides by -10

m  =  -50 / 10   =   -5