Aradio station had 155 tickets to a concert. they gave away 4 times as many tickets to listeners as to employees. how many tickets did they give away to employees?

4(employees) = listeners
listeners + employees = 155
plug the first equation into the second, substituting 4(employees) for listeners, so 
4(employees) + employees = 155.
5(employees) = 155
employees = 31