When we substitute a number for a letter, we simply replace the letter with the number.
Example
Work out the value of the following expression when a = 4 and b = 9
3a | + | 4b |
2 | 3 |
Answer
We substitute a = 4 and b = 9 into the following expression:
3a | + | 4b |
2 | 3 |
= | 3 x 4 | + | 4 x 9 |
2 | 3 |
= | 12 | + | 36 |
2 | 3 |
= 6 + 12 = 18
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