Question

At dee dee's dinette the probability that a customer orders coffee is 0.60, the probability that a customer orders pie is 0.35, and the probability that a customer orders neither coffee nor pie is 0.30. find the probability that a customer orders both coffee and pie.

Answer 1

For better understanding think of it this way. There are hundred customers, 60 orders coffee 35 orders pie and 30 does not order pie or coffee. 
This means that 70 does order coffee or pie or both. Out of those 70 people 10 will not order coffee and 35 will not order pie. Thus 70-10-35=25 will order both coffee and pie. 
P=0.25