A linear equation has the form y=mx+c.
In the first set you are given m. Substitute the points and then rearrange to find c. So for the first question,
y = -2x+c and (x,y) = (2,1)
1 = -2(2)+c
y = -2x+5
In the second set you are given 2 points. Call them and , and use the formula , then use the method for the first set.
The first question looks like this:
y = 2x+c
3-4 = c