Answer:5/9 miles (Problem 14) or 1/6 cup oil (Problem 15)
Explanation:
This is a fraction addition/subtraction problem, so you will need the fraction denominators (the bottom numbers) to be equal. To convert 2/3 to a fraction in ninths, multiply the top and bottom by 3 to get 6/9. Once you know that the bike ride is usually 6/9 miles and the shortcut took off 1/9 of a mile, you can simply subtract the two.
For the next problem, you must convert the numbers to fractions with common denominators yet again. However, 2 and 3 cannot easily multiply into one another. However, what you can do is multiply the denominators by themselves, or a smaller number that they both multiply into. In this case, multiply the top and bottom of 1/2 by 3, and the top and bottom of 1/3 by 2. This will give you 3/6 and 2/6, respectively. You are asked to find the difference between the oil used for brownies (3/6) and the oil for muffins (2/6).
\frac{3}{6} - \frac{2}{6} = \frac{1}{6}