Answer: 225
Step-by-step explanation: if there are 510 hamburgers and cheeseburgers in total and there are 60 more cheeseburgers then hamburgers, we can use that that to make an equation. We can have hamburgers be X, and cheeseburgers be x+60. Using that, we can form the equation x+x+60=510. Then we solve that:
x+x+60=510
2x+60=510
2x=450
x=225
now we know that there were 225 hamburgers