Help please?

Afruit stand has to decide what to charge for their produce. they need $10 for 4 apples and 4 oranges. they also need $15 for 6 apples and 6 oranges. we put this information into a system of linear equations. can we find a unique price for an apple and an orange?

Can some one me with these questions

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?