=>

Since the car travelled for 15 minutes with the speed 40 mph, it moved 10 miles. It take 20 minutes the bicycle to travel 10 miles with the speed 30 mph.

Therefore, the answer is B.
Answer: B

speed rate of car = 40 mph
speed rate of bicycle = 30 mph
15 minutes to an hour = 1/4 hour
In 15 minutes, the car ha travelled $$40\cdot\frac{1}{4}=10miles$$
and the bicycle travelled $$30\cdot\frac{1}{4}=\frac{30}{4}miles$$
At constant speed, the bicycle will have to travel additional miles to reach the position of the car
$$Therefore\ \frac{10}{1}-\frac{30}{4}=\frac{40-30}{4}=\frac{10}{4}=\frac{5}{2}miles$$
i.e bicycle will travel additional 5/2 miles to reach the car.
if the bicycle travels 30 miles in 60 minutes
it will travel 5/2 miles in x meter
$$30=60$$
$$\frac{5}{2}=x$$
by cross multiplying
$$30\cdot x=60\cdot\frac{5}{2}$$
$$\frac{30x}{30}=\frac{150}{30}$$
$$x=5miles$$
Bearing in mind that the bicycle has already travelled 15 minutes
Total time-taken to reach waiting point = 15+5 mile = 20 miles
$$Option\ B$$