x = 1st class and y = coach
x + y = 12...x = 12 - y
1160x + 130y = 9800
1160(12 - y) + 130y = 9800
13920 - 1160y + 130y = 9800
-1160y + 130y = 9800 - 13920
- 1030y = - 4120
y = -4120/-1030
y = 4 <==== coach tickets
x + y = 12
x + 4 = 12
x = 12 - 4
x = 8 <== first class tickets