c = number of coach tickets
f= number of first class tickets
c + f = 12 ( number of tickets
290c + 970f = 7560 cost of tickets
c=12-f solve first equation for c and then substitute it into the second equation
290(12-f) + 970f = 7560
3480 - 290f + 970f = 7560
3480 + 680f =7560
680f = 4080
f= 6
6 first class tickets
to check
c+f=12 c + 6=12 c = 6
290(6)+970(6)=7560
7560 = 7560 is true
6 first class tickets
Jacob D.
10/18/17