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 \(R\) is located at \((3,\text-2)\). This means \(R\) is 3 units to the right and 2 units down from \((0,0)\).

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 \(435+60=495\).

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 \(\text-3 > \text-7\) 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 \(\frac81\) and \(\text-\frac81\).
• 0.75 and -0.75 are rational numbers because they can be written as \(\frac{75}{100}\) and \(\text-\frac{75}{100}\).

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 \(m+1=8\) is 7, because it is true that \(7+1=8\).
• The solution to \(m+1=8\) is not 9, because \(9+1\) 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 \(10-x\), the variable is \(x\).

• If the value of \(x\) is 3, then \(10-x=7\), because \(10-3=7\).
• If the value of \(x\) is 6, then \(10-x=4\), because \(10-6=4\).

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 \(350-25=325\).