Which equation would you use to solve the following situation?

Molly buys some concert tickets at $10 each. If she spends $90 on the tickets, how many did she buy?

90 - t = 10

10t = 90

10 + 90 = t

9t = 90

You would use the last one, because each ticket is $10 and you want to see how many tickets she could buy. Although the way to work it out would be:

90 / 10 = 9

This is because you're told the price and how much they cost individually.