Part A: She burns 10 calories in 3 minutes and she ends up burning 40 calories. Let x = number of minutes she needs to burn 40 calories. Then 40/10 = x/3. Therefore, 4 =x/3, multiply both sides of the = sign by 3, and you arrive at 12=x. She needs 12 minutes to burn 40 calories.
How many miles has she travelled? First determine how many kilometers she travelled. She rode her bike for 12 minutes, and she goes at the rate of 24 kilometers per hour. Let's see what part of an hour 12 minutes is. 12 minutes / 60 minutes per hour = 1/5 hour. So 1/5 * 24 = 4.8 kilometers. That's how far she travelled to burn 40 calories.
Next we need to know how many kilometers are in a mile. The answer, to two decimal places, is 1.61. So, 4.8 km / 1.61 km per mile = 2.98 miles.
Part B. It takes 2.98 miles to burn off 40 calories, and the Starbucks drink is 440 calories. Let m = number of miles to burn off the Starbucks. Then 440/40 = m / 2.98 miles
11 = m / 2.98 miles
11 * 2.98 miles = m
32.78 miles = m
Kind of uneven numbers to a school question, but there you are.