so we distribute the 2 to the 3m and the +4 so
2*3m=6m
2*4=8
6m+8
we then distribute the 3 to the m and the - 5
3*m=3m
3*-5=-15 ((+) times (+) or (-) times (-)=(+), (-) times (+) or (+) times (-)=(-))
3m-15
add 6m+8 and 3m-15
6m+8+3m-15
add like terms (m terms + m terms and number + numbers)
6+3=9 so
3m+6m=9m
9m-7