So,
#1:

Convert to like improper fractions.

Add.

So, one solution could be

.
Another solution could by 9. There is also 10, 11, 12, etc., and all numbers in between.
#2:

Convert into improper fraction form.

Multiply.

Cross-cancel, and we have our final result.

k < 96
96 is not a solution.
95 is a solution.
So is 94, 93, 92, etc, and all numbers in between.
The correct answer to your question is C.
0<r<6
the least number of ride he can go on is 0 which is none and the most is 6 because 15/2.50=6
By definition of conditional probability,
P(B | A) = P(A ∩ B)/P(A) = (13/25) / (13/20) = 20/25 = 4/5