Inactive Tutor answered 03/12/15
Tutor
New to Wyzant
Let x be the number of first class and 7-x be the number of coach tickets.
980x +170(7-x) ≤ 2810
980x +1,190 -170x ≤ 2810
810x ≤ 1620
x ≤ 2
So either she bought 0, 1, or 2 first class tickets and 7, 6 or 5 coach tickets respectively.
0(980) + 7(170) < 2810 Less than her budget, but 1620 left over!
That's enough for 2 first class tickets!
1(980) + 6(170) > 2810 Too much for her budget!
2(980) + 5(170) = 2810 Her budget exactly!
She bought 5 coach tickets and 2 first class.
5(170) +2(980) = 2810