SOLVED Enter number and lookup matched subject

I have the following scenario and am stuck on how I need to complete my task at hand.

I have two sheets. The first sheet has three columns. A: is the name of a student B: is the subject C: is the grade
The Second sheet has two columns A: is a number B: is a subject that corresponds to each Column A number

So what I want is to be able to type in a number in the first sheet under Column B and have the input be the subject (math, english, ect)

Not quite sure where to start with this.

any help will be appreciated!