When we substitute a number for a letter, we simply replace the letter with the number.
However, we must remember that 4b means 4 x b.
Example
Work out the value of the following expression when a = -4
3a - 7
Answer
3a - 7
= (3 x a) - 7
= (3 x - 4) - 7
= -12 - 7
= -19
This activity contains 10 questions
