Question

slope=1/2 through (-1,-3)

Answer 1

y = (1/2) x - 5/2

Answer 2

notice that (-1,-3) works:
-3 = (1/2) (-1) - 5/2

Answer 3

could you give me an example how you got the answer

Answer 4

set y = (1/2) x + b because you know the slope (1/2) but not the intercept (b)
then plug in x and y (x=-1, y=-3)
solve for b
done.