> At a university, 28% of the students major in zoology. Of all the students majoring in zoology, 68% are males. It is also known that 56% of all students at the university are male.
>
> Let Z represent the event that a randomly chosen student is majoring in zoology. Let M represent the event that a randomly chosen student is male.
Write down what you do know. $\mathsf P(Z)=0.28, $ and so on.
> (a) What is the probability a randomly chosen student is male and majoring in zoology?
You seek $\mathsf P(M\cap Z)$. Express that in terms of what you do know and evaluate.
$$\mathsf P(M\cap Z) = \mathsf P(M\mid Z)\;\mathsf P(Z)$$
And so forth.