Start with the point-slope form:
.
Then you substitue in the slope and coordinates from the point:

You don't do a lot of clean up to the form, with the exception of turning "minus negative 7" into "plus 7".

Thar be yer answer!
The answers to the questions
4 cups = 18 g
Divide all by 4 to get 1 cup.
1 cup = 18/4
1 cup = 4.5g
The answer is 5.50$ you have to divide 16.50/ 3
There is no solution
Hope this helps :)