An equation tells us that two things are equal.

To solve an equation we need to find out what a missing number is.

Here is an equation:

a + 9 = 15

a is a missing number. To solve this equation we need to work out what number a is.

Because both sides of the equation are equal if we do the same thing to both sides the equation will still be equal.

At the moment we have 9 added onto a. To get a by itself we can do the opposite of adding 9, subtracting 9. If we subtract 9 from both sides of the equation we have:

a + 9 - 9 = 15 - 9

a = 6

We have solved the equation and found that a = 6

**Example 1:Solve: b - 12 = 8**

We can add 12 to both sides of the equation to get b by itself

b - 12 + 12 = 8 + 12

b = 20

**Example 2:Solve: 5c = 45**

5c means 5 × c

The opposite of multiplying by 5 is dividing by 5

To get c by itself we can divide both sides by 5.

c = 9

**Example 3:Solve: d⁄ 3 = 12**

5c means 5 × c

The opposite of dividing by by 3 is multiplying by 3

To get d by itself we can multiply both sides by 3.

d = 36

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