Solve the equation in the photo above

How do you use the additive inverse to evaluate an expression that uses subtraction in a full sentence

How many of the 250 grandparents in the population would you expect to prefer online shopping with merchant a? merchant a: 4 merchant b: 6 merchant c: 2 merchant d: 3 other: 5 none: 5 answer choices: a.about 4 b.about 8 c.about 40 d.about 21

Thelime contains the point(-3,0) and parallel x-3y=3( show all work)