Standard Norm. Distribution Curves

Ive been studying for a test ive got tomorrow, and i keep getting stuck on questions that i should know by now.-_-. heres some of them.

Find the z value to the right of the mean so that:

a. 53.98% of the area under the distribution curve lies to the left of it.

b. 71.90% ' '

c. 96.78% ' '

Im using my TI-84 but i also have a normal distribution chart thing. I wasnt sure how to approach this kind of problem. I have a memory of doing them in class, but once im out of class its over.--_--

thanks for the help