To solve for the equations of these graphs all you simply do is get two points located on the line. In the case of the first one (Question 24): (-2,2) and (1,0). Now you label each point as a value x1 or x2 or y1 or y2. In this case -2 will be x1 and 2 will be y1. Since x1 and y1 are now taken up 1 will be x2 and 0 will be y2.
Now we find the gradient: y2 - y1 / x2 - x1
This gives us 2 / -3 or -2/3
We then sub it into the equation formula
y - y1 = m(x - x1) [M is the gradient]
y - 0 = -2/3 (x + 2)
and you can take it from there