To simplify (5m+3n)-(2m-n) you will have to subtract the same numbers in this case so 5m-2m will give you 3m, 3n even though you aresubs tracking it in this case since n has a minus sign in front of it that will make it positive number with the minus in the middle so you would do 3n+n which will give you 4n which the simplified answer would be 3m-4n