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.
5c⁄5 = 45⁄5
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.
3d⁄3 = 12 × 3
d = 36
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