The absolute value of a number is its distance from 0 on the number line.

• The absolute value of -7 is 7, because it is 7 units away from 0.
• The absolute value of 5 is 5, because it is 5 units away from 0.

The coordinate plane is one way to represent pairs of numbers. The plane is made of a horizontal number line and a vertical number line that cross at 0.

Pairs of numbers can be used to describe the location of a point in the coordinate plane.

Point is located at . This means is 3 units to the right and 2 units down from .

A deposit is when money is put into an account.

For example, a person added $60 to their bank account. Before the deposit, they had $435. After the deposit, they had $495, because .

An inequality is a statement that compares two values or expressions using symbols such as “” or “”. 

• The symbol “” means “is greater than.”
• The symbol “” means “is less than.”

For example, the inequality  tells us that -3 is greater than -7.

A negative number is a number that is less than 0.

Two numbers are opposites if they are the same distance from 0 on the number line, but on different sides. One is negative, and the other is positive.

A positive number is a number that is greater than 0.

The coordinate plane is divided into 4 sections called quadrants. The quadrants are numbered using Roman numerals, as shown.

A rational number is a number that can be written as a positive fraction, a negative fraction, or zero.

• 8 and -8 are rational numbers because they can be written as and .
• 0.75 and -0.75 are rational numbers because they can be written as and .

The sign of any number other than 0 is either positive or negative.

For example, the sign of 6 is positive. The sign of -6 is negative. Zero does not have a sign, because it is not positive or negative.

A solution to an equation is a number that can be used in place of the variable to make the equation true.

• The solution to the equation is 7, because it is true that .
• The solution to is not 9, because does not equal 8. 

A variable is a letter that represents a number. Different numbers can be chosen for the value of the variable.

In the expression , the variable is .

• If the value of  is 3, then , because .
• If the value of  is 6, then , because .

A withdrawal is when money is taken out of an account.

For example, a person took out $25 from their bank account. Before the withdrawal, they had $350. After the withdrawal, they had $325, because .