+ | X Y Z

4 | 1 -5 m

e | 7 n 10

f | 2 -4 5

In the addition table shown above, what is the value of m+n?

对表格看不懂，上面我画了两个。第一行下面和第一列右则有条线，希望各位NN能给予指点，多谢！

z + e = 10

4 + y = -5

So, m + n = (4 + z) + (e + y) = (4 + y) + (z + e) = -5 + 10 = 5