3m - 9n = 24; n = - 1,1,3

given that

3m - 9n = 24

when n = - 1

substitute it in the equation

thus

3m - 9 (-1) = 24

solving for m

3m + 9 = 24

3m = 24-9

3m=15

dividing through by 3

3m/3 = 15/3

m = 5. thus when n = - 1, m=5

also put n=1 into the equation

3m - 9 (1) = 24

3m - 9 = 24

3m = 24+9

3m = 33

dividing through by 3

3m/3 = 33/3

m=11

thus when n = 1, m=11

lastly, put n = 3 into the equation

3m - 9 (3) = 24

3m - 27 = 24

3m = 24+27

3m = 51

dividing through by 3

3m/3 = 51/3

m = 17. Thus when n = 3, m = 17.