There are 3*infinity possible integer solutions:
a = n_1+n_2-n_3-n_4-n_5-n_6-n_7-1, b = -n_1+n_3+n_4+n_8+n_9-n_10-n_11, c = -n_1+n_4+n_5+n_9-n_10+n_12-n_13, m = n_2-n_7+n_8+n_9-n_10+n_12+n_14, n_1 element Z, n_1 >=0, n_2 element Z, n_2 >=0, n_3 element Z, n_3 >=0, n_4 element Z, n_4 >=0, n_5 element Z, n_5 >=0, n_6 element Z, n_6 >=0, n_7 element Z, n_7 >=0, n_8 element Z, n_8 >=0, n_9 element Z, n_9 >=0, n_10 element Z, n_10 >=0, n_11 element Z, n_11 >=0, n_12 element Z, n_12 >=0, n_13 element Z, n_13 >=0, n_14 element Z, n_14 >=0,
a = n_1+n_2-n_3-n_4-n_5-n_6-n_7, b = -n_1+n_3+n_4+n_8+n_9-n_10-n_11-1, c = -n_1+n_4+n_5+n_9-n_10+n_12-n_13-1, m = n_2-n_7+n_8+n_9-n_10+n_12+n_14, n_1 element Z, n_1 >=0, n_2 element Z, n_2 >=0, n_3 element Z, n_3 >=0, n_4 element Z, n_4 >=0, n_5 element Z, n_5 >=0, n_6 element Z, n_6 >=0, n_7 element Z, n_7 >=0, n_8 element Z, n_8 >=0, n_9 element Z, n_9 >=0, n_10 element Z, n_10 >=0, n_11 element Z, n_11 >=0, n_12 element Z, n_12 >=0, n_13 element Z, n_13 >=0, n_14 element Z, n_14 >=0, and
a = n_1+n_2-n_3-n_4-n_5-n_6-n_7, b = -n_1+n_3+n_4+n_8+n_9-n_10-n_11, c = -n_1+n_4+n_5+n_9-n_10+n_12-n_13, m = n_2-n_7+n_8+n_9-n_10+n_12+n_14+1, n_1 element Z, n_1 >=0, n_2 element Z, n_2 >=0, n_3 element Z, n_3 >=0, n_4 element Z, n_4 >=0, n_5 element Z, n_5 >=0, n_6 element Z, n_6 >=0, n_7 element Z, n_7 >=0, n_8 element Z, n_8 >=0, n_9 element Z, n_9 >=0, n_10 element Z, n_10 >=0, n_11 element Z, n_11 >=0, n_12 element Z, n_12 >=0, n_13 element Z, n_13 >=0, n_14 element Z, n_14 >=0.
I copied that from WolframAlpha.
Everyone (EDIT: Soranz) please stop making up your own algebra. XD
If we're told:
A+B < M1
A+C < M1
then we basically know nothing.
Soranz, you may be interested to know that multiplying by a negative number changes the direction of the inequality sign, and multiplying by 0 makes it an equals sign.
Simply adding the equations together will only lose us information from the two inequalities, and garners:
2 A + B + C < 2 M1
Which is true, but less specific than the original set of equations and therefore less helpful.
Algebra isn't magic, if you're given no real information to work with it can't generate magic answers, unfortunately.