The charge for admission into the concert is $2.75 for adults and $1.50 for childeren. If 589 people paid to get into the concert and $1151 was collected, find the number of adults and the number of childeren who paid for tickets.
solve
a + c = 589 with 2.75a + 1.5c = 1151
I suggest changing the first to
a = 589-c and subbing that into the second