I'm still confuse about these events. Also 180 + 160 is more than 300. Where have I made the mistake?

The owners of a music store placed ads in the newspaper and on TV advertising their annual 40% sale. They did a survey of the first 300 customers, and discovered that 180 saw the ad on tv, 160 saw the ad in the newspaper and 75 saw the on TV and in the newspaper. What is the probability that a randomly select customer

a. saw the advertisement in the newspaper and on Tv?

75/100

b. saw the advertisement in the newspaper or on TV?

P(AandB) = P(A) + P(B) = 160/300 + 180/300 - (it is not a probability!!)

c. did not see the ad?

P(AorB) = P(A) + P(B) - P(AandB)= 160/300 + 180/300-??

Please help