We can calculate the line equation with two points the following manner:

For problem 19, we have:

For problem 20, we have:

For problem 21 and 22, we have to graph the equations, to do that we need to find two points on the line.
For problem 21, we can choose x = 2 and x = 3 and found the respective y-value:

With the points (2, -3) and (3, -1) we can graph the line: