**Substitution**

**Substitution In Algebra**

**What is a substitution?**

Replacing the letter representing a variable by a number.

Here is an example of substitution:

Area of rectangle = l × w

where l is the length of the longer side

and w is the length of the shorter side.

In a particulat rectangle

we may know that l = 5 and w = 3

**Why did you use brackets?**

To make things clearer and to reduce the risk of a mistake.

Yes, that was an easy example,

but sometimes we have negative numbers as substitutions and we can make sure that we capture the negative sign inside the brackets so that it does not get lost or used incorrectly.

Also, we may have a more complicated formula to put them in.

Can you show me a more complicated one please?

Certainly, lets do one with three substitutions

where one of them is negative.

**Example:**

y = m × x + c

find the value of y when m is 2, x is 10 and c is -6