Question 84358
Problem#1:
K is the 5x2 zero matrix!

Problem #2:

{{{(matrix(2,3,a+2,3z+1,5m,4k,0,3))+(matrix(2,3,3a,2z,5m,2k,5,6)) = (matrix(2,3,10,-14,80,10,5,9))}}},
This means
a+2+3a = 10, or 4a = 8, or a = 2.
3z+1+2z = -14, or 5z = -15, or z = -3,
5m+5m = 80, or 10m = 80, or m = 8, and 
4k+2k = 10, or k = 10/6 = 5/3.