This equation shows how rosa's bank account balance is related to the number of raffle tickets she purchases. d = -3.4r + 63.6 the variable r represents the number of raffle tickets she purchases, and the variable d represents the balance of her bank account. how many tickets does rosa need to buy to get the account balance down to $22.80?

So we know that  is the number of raffle tickets she purchases and  is the balance of her bank account.

We are given the equation  and we want to get the down to $22.80. So since  represents the account balance just plug in $22.80 for d and solve for r. 

When you do that you should get .

So, Rosa will need to buy 12  tickets to get her account balance down to $22.80.