Your new line has to have the same slope as the green line for them to be parallel, so start off with y=-3/4x+b.
Plug in (2,4) into the new line so 2 for x and 4 for y
It should look like 4=-3/4(2)+b
-3/4x2 is -1.5
Then add 1.5 to both sides and you should get 5.5=b
Your new line is y=-3/4x+5.5 and (0,5.5) is a point on the line