A cross-country racer travels 20 kilometers before she realizes that she has to cover at least 75 kilometers in order to qualify for the next race. if the racer travels at a rate of 10 kilometers per hour, how many whole hours will it take her to reach the 75-kilometer mark?

So find how much the racer needs to cover more

she covered 20 and needs to cover 75

75-20=55

she needs to cover 55 more

so 10 km per hour

10 times x hours=55 miles

divide both sides by 10

x hours=5.5

since you want whole hours, we round up so she at least gets there

6 hours is the answer