Final answer:
Sarah bought 7 first class tickets and 5 coach tickets.
Step-by-step explanation:
To find how many first class tickets and coach tickets Sarah bought, we can set up a system of equations:
Let x be the number of first class tickets and y be the number of coach tickets.
We know that the total number of people who took the trip including Sarah is 13, so x + y + 1 = 13.
We also know that the total cost of the tickets is $8990, so 1190x + 110y = 8990.
We can solve this system of equations to find the values of x and y.
Multiplying the first equation by 110, we get 110x + 110y + 110 = 1430.
Subtracting this equation from the second equation, we get 1190x - 110x = 8990 - 1430.
Simplifying, we get 1080x = 7560.
Dividing both sides by 1080, we find that x = 7.
Substituting this value into the first equation, we can solve for y: 7 + y + 1 = 13.
Simplifying, we find that y = 5.
Therefore, Sarah bought 7 first class tickets and 5 coach tickets.