Each (~) is the start of a different line. I guess this system doesn't like the format I tried to do. ~4.2 is your starting amount ~0.6 is the difference between the set of numbers you gave ~4.8-4.2=0.6 ~5.4-4.8=0.6 ~6.0-5.4=0.6 ~(x-1) is for each number you want to find ~You have terms 1-4 and you are looking for terms 5-7 ~So you have the equation y=4.2+0.6(x-1) ~y=4.2+0.6(5-1)=6.6 ~y=4.2+0.6(6-1)=? ~y=4.2+0.6(7-1)=?