When you know the value for letters in an algebraic expression you can substitute these values into the expression and solve it.

**Substitution**means putting numbers in place of letters to calculate the value of an expression.- An
**expression**can be a combination of numbers, letters and operators, grouped together.

Look at the examples below:

**If** \(a~=~2\) **and** \(b~=~5\)

**Find** \(3a~+~2b\)

How to solve the expression:

\(3a~+~2b\)

Substitute \(a\) with the value \(2\) and \(b\) with \(5\)

\[{3}\times{2}~+~{2}\times{5}\]

\[=~6~+~10\]

\[=~16\]