Evaluate solutions when there are Two Unknowns in an Expression

In this activity, we will substitute values of unknowns to evaluate an expression. 

To substitute just means to swap something

Like with football - one player comes off the pitch and one comes on in their place!

They are swapped!

Let's have a look at an example.

Example

When a = 5 and b = 10 

What is the value of 2a + 4b?

Answer

2a + 4b = (2 x a) + (4 x b)
When a = 5 and b = 10 we substitute them 
(2 x 5) + (4 x 10)
= 10 + 40
= 50

Let's try some of these - be very careful with any negatives!