Evaluate: 15=-3m+18+5m-7

Expression: $15=-3m+18+5m-7$

Collect like terms

$15=2m+18-7$

Subtract the numbers

$15=2m+11$

Move the variable to the left-hand side and change its sign

$15-2m=11$

Move the constant to the right-hand side and change its sign

$-2m=11-15$

Calculate the difference

$-2m=-4$

Divide both sides of the equation by $-2$

$m=2$