Adding and subtracting fractions with unlike denominators

The  exercise appears under the 5th grade (U.S.) Math Mission. This exercise practices adding and subtracting fractions with unlike denominators.

Types of problems
There is are two types of problem in this exercise:
 * 1) Find the missing fraction.: This problem has an equation, such as $$\frac{x}{y}+\frac{3}{4}=\frac{15}{20}$$, and user is asked to find the missing fraction by adding or subtracting.
 * 2) Solve:: This problem has the user add and subtract three fractions. User is asked to find the answer and type it in the text box.

Strategies
Basic knowledge of adding and subtracting fractions is required for this exercise.
 * 1) Since the fractions in this exercise have unlike denominators, user has to list the multiples of the denominator to find the common denominator so they can find the missing fraction.

Real-life Applications

 * 1) Fractions, decimals, and percents are used in many sports such as basketball to determine how many field goals the player has made over how many they missed.