Adding and subtracting fractions with unlike denominators challenge

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 one type of problem in this exercise:
 * 1) Find the missing fraction: This problem asks the user to find the missing fraction that would make the equation true.
 * 2) Solve: This problem has three fractions and may have the user both add and subtract some of them.

Strategies
Basic knowledge of adding and subtracting fractions are required for this exercise.
 * 1) There are unlike denominators in this exercise, so before user does the problem, they should make equivalent fractions with a common denominator that is a multiple of both denominators.

Real-life Applications

 * 1) Fractions are used for sales, such as a television set that is on sale for half ($$\frac{1}{2}$$) of its price.