Question

What is the value of a in the equation 3 a plus b equals 54, when b equals 9?

15
18
21
27

Answer 1

`3a+b=54`

`3a+9=54\:[b=9]`

`3a=54-9`

Subtract 9 from both sides

`3a=45`

Divide both sides by 3

`(3a)/(3)=(45)/(3)`

`a=15`

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Answer 2

a=15

Explanation:

3a+b = 54

Let b=9

3a+9 = 54

Subtract 9 from each side

3a+9-9= 54-9

3a = 45

Divide each side by 3

3a/3 = 45/3

a = 15