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.

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 \(\text-\frac{75}{100}\).

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 \(350-25=325\).