Answer:
m = - 5
Explanation:
sum the first row
1 - 10 - 2 = 1 - 12 = - 11
sum the third row
- 17 + 19 - 13 = 2 - 13 = - 11
the second row must then sum to - 11 , that is
5 + 4m + 4 = - 11
9 + 4m = - 11 ( subtract 9 from both sides )
4m = - 20 ( divide both sides by 4 )
m = - 5