Algebra is used in equations to express mathematical relationships
where quantities (amounts) are unknown, and are usually represented
therefore by symbols like letters e.g. X or Y

(Equations are mathematical statements)

Here is a simple example :

X + 6 = 10
Something plus six equals ten

In this example we can work out what X is
We simply take six away from ten

X = 10 - 6
.^.. X = 4
(.^.. = Therefore)