If she made a 90 that means 90 percent aka .90 so multiply that by 60 to get 54 right aka 6 wrong which you could find either by subtracting 54 from 60 or solving for 10 percent bc she got that much wrong and multiply .10x60=6 wrong
The markup price is $9.6
You will be paying 120% which is 1.20 as a decimal
So you multiply. 8(1.20) which gives you $9.6
The answer is approximately 4.308.