Agas station offers two ways to pay for oil changes. plan 1: pay $30 per oil change. y = 30x plan 2: pay $60 for the first oil change and $15 for every oil change after the first. y = 15x + 60 at how many oil changes will the cost for both plans be equal?

For plan 1 we have the following equation:
 
 For plan 2 we have the following equation:
 
 The variables are defined as:
 x: number of oil change
 y: total cost
 Equating the cost of both plans we have:
 
 From here, we clear the value of x.
 We have then:
 
 
 The cost for both plans will be equal at 4 oil changes