One way is to type it into your trusty TI and use the table from presing stat and then stat againg then calc then 4
so the equation that I got from your set of points is y=1.983333333333333x+0.80555555555
Step 3 is the frist incorrect step it should be: 2x-3=3 or 2x-3=-3
Im just about to work one out for you and you just do the same on the rest
2 and 3/4 is a mixed number and the decimal of it is 2.75
3,000 y / 15 m
9,000 f / 15 m
X f / 6 m = 9,000 f / 15 m
Cross multiply
3,600 feet