Evaluating expressions
The question
2x − 8
Work out the value of the expression.
2x − 8, x = 5
2x − 8withx = 5
2 × 5=10
10−8=2
2x − 8=2
- We are told x = 5. Put each value in where its letter is, in brackets.
- 2x means 2 times x, and multiplying comes before adding or taking away: 2 × 5 = 10.
- Now the last bit: 10 − 8 = 2.
- So 2x − 8 is 2 when x = 5.
How it works.
- 01
We are told x = 5. Put each value in where its letter is, in brackets.
- 02
2x means 2 times x, and multiplying comes before adding or taking away: 2 × 5 = 10.
- 03
Now the last bit: 10 − 8 = 2.
- 04
So 2x − 8 is 2 when x = 5.