Final answer:
To solve the problem, use a system of equations. The solution is 3 first-class tickets and 9 coach tickets.
Step-by-step explanation:
To solve this problem, we can use a system of equations. Let C represent the number of coach tickets and F represent the number of first-class tickets. We know that C + F = 12, since the total number of people on the trip is 12.
We also know that 290C + 1270F = 6420, since the total cost of coach tickets and first-class tickets is $6420. We can use these equations to solve for the values of C and F.
One way to solve this system of equations is by substitution. We can solve the first equation for C and substitute it into the second equation:
C = 12 - F
Substituting this into the second equation:
290(12 - F) + 1270F = 6420
Expanding the equation:
3480 - 290F + 1270F = 6420
Combining like terms:
980F = 2940
Dividing by 980:
F = 3
Plugging this value back into the first equation, we find that C = 12 - 3 = 9.
Therefore, Sarah bought 3 first-class tickets and 9 coach tickets for the trip.