$-4m-16=-4-8m+8$
Calculate the sum$-4m-16=4-8m$
Move the variable to the left-hand side and change its sign$-4m-16+8m=4$
Move the constant to the right-hand side and change its sign$-4m+8m=4+16$
Collect like terms$4m=4+16$
Add the numbers$4m=20$
Divide both sides of the equation by $4$$m=5$