Idon’t know whether to add or subtract in word problems with fractions me

43lbs of tomatos cost $387. how much would 41lbs cost

Multiplying fractions by whole number 5 x 1/3=?

Charlie is at an amusement park that has 18 different rides. each ride costs $1.75. the function c(r) = 1.75r represents the total amount of money that charlie will spend if he goes on r rides, but he never goes on the same one more than once. what domain and range are reasonable for the function?