The cost of bottles of vitamins varies directly with the number of vitamin
tablets in a bottle. A bottle of 50 vitamin
tablets costs $12. What is the cost in
dollars of a bottle of 75 vitamin tablets?

find cost of one vitamin tablet first

50/12 = 4.2

therefore $4.2 is the cost for one tablet

now to find the cost of 75 vitamin tablets we just need to multiply the cost of one tablet with 75.

75*4.2=315

therefore the cost of a bottle of 75 vitamin tablets is $315