I need help. Thanks!

For the first case we know that 100 tablets of 50 mg each costs $75
So cost of 1 tablet = 75/100 dollar
                             = 0.75 dollar
Now cost of 1 mg in this case is = 0.75/50 dollar
                                                     = .015 dollar
For the second case we know that 85 capsules of 75 mg each costs $63.75
So cost of 1 capsule = 63.75/85 dollars
                               = 0.75 dollar
Now cost of 1 mg of capsule in this case = 0.75/75 dollars
                                                                   = 0.010 dollars
For the third case we know that 40 caplets of 100 mg each cost $70
So cost of 1 caplet = 70/40 dollar
                                = 1.75 dollar
Now cost of 1 mg of caplet in this case = 1.75/100 dollars
                                                               = .017 dollars
So the costliest among all the medicines are the caplets.