To calculate K, we use the following:
If you move a units in y for every b units in x, K= a/b
Let's use this in the four graphs:
For graph 1, notice that if we move 1 unit in x, we move 1 unit in y
Thereby, K=1
For graph 2, notice that if we move 1 unit in x, we move 7 units in y
Thereby, K=7
For graph 3, notice that if we move 9 units in x, we move 4 units in y
Thereby, K=4/9
For graph 4, notice that if we move 2 units in x, we move 10 units in y
Thereby, K=5