Before taking the Military Flight Aptitude Test, one subject area you should review is basic algebra. Algebra is a fun subject in which letters represent variables, and your role is to find out exactly what that variable stands for.

The most common algebraic variable is x, which is why you often hear the phrase “solve for x” in reference to unknown quantities. But you can use any variable you like as long as the same variable represents only one quantity throughout a given problem.

Algebra deals in equations, or statements that two given quantities are equal. 16 + 17 = 33 is an equation. In algebra, equations include variables that you have to solve for. Here’s an example problem: Three fuel tankers, each carrying 2,000 gallons of jet fuel, completely empty their loads to fill up an empty tank. How much fuel total is in the tank?

Let T stand for the fuel in the tank and F stand for the fuel in one tanker. You can use these variables to create an algebra formula of T = 3F for this problem. You know that F = 2,000 gallons, so you can substitute that into the equation to get T = 3 x 2,000 gallons, or T = 6,000 gallons.

The four arithmetic operations (addition, subtraction, multiplication, and division) are all possible in algebra. You can express each operation through algebra equations as follows:

• The sum (addition) of two numbers x and y is written as x + y.

• The difference (subtraction) between two numbers x and y is written as xy.

• The product (multiplication) of two numbers x and y is written as xy or x x y.

• The quotient (division) of two numbers x and y is written as x/y or x ÷ y.

You can perform any calculation on either side of an equation as long as you do it to both sides of the equation.