I hope you guys can help me... because it's easy but for some reason I can't figure it out? -.-

1) Two hundred people attend a concert. The total receipts are $4500. If one student ticket costs $5, and one adult ticket costs $30, find the number of students who attend the concert?

2) A farmer raises some pigs and chickens. Among the pigs and chickens there are 24 heads and 64 feet. How many pigs and chickens are there?

Substitution only please.

Come to think of it... maybe you guys can just do one and I can use your steps from the first one to do second :)