Let x be the number of oil changes she does.
Let y be the number of tire changes she does
From the information given,
it takes her 9 minutes to do an oil change. This means that the number of minutes it will take her to do x oil changes is 9 * x = 9x minutes
Also, it takes her 15 minutes to do a tire change. This means that the number of minutes it will take her to do y tire changes is 15 * y = 15y minutes
Given that the total time should be less than 60 minutes, the inequality describing how many oil changes and tire changes Lella can do in less than an hour (60 minutes) is
9x + 15y < 60