I am having problems solving this problem, can you help?

John and Mary are taking a mathematics course. The course has only three grades: A, B, and C. The probability that John gets a B is 0.3. The probability that Mary gets a B is 0.4. The probability that neither gets an A but at least one gets a B is 0.1. What is the probability that at least one gets a B but neither gets a C?

The problem as written is incorrect. If the probability that John gets a B is .3, and Mary gets a B is .4, then the probability that John and Mary both get a B is .3 * .4 = .12 (assuming these are independent events). But this is inconsistent with the next sentence, since the probability of neither getting an A but at least one gettting a B must be greater than (or at least equal to) .12.

I have a problem answering this question can you help?

Suppose 50% of the cars are manufactured in the United States and 15% of these are compact; 30% of the cars are manufactured in Europe and 40% of these are compact; 20% are mabufactured inJapan and 60% of these are compact. If a car is picked at random from a lot, find the probability that it is a compact

In the future please do not tack a new question onto an old thread - you should start a new thread instead.

The probability that a car chosen at random is a compact is the sum of the probability that the car is US compact + the probability that the car is European compact + the probability that the car is a Japanese compact. Starting with the fuirst term: the probability of a car chosen at random is a US compact is equal to the probability that the car is from the US times the probability that a US car is a compact:
P(car chosen at random is a US compact) = 0.5 x 0.15 = 0.075.

Can you complete it from here?