Question

How do you solve `3x + 6 = 21`?

Answer 1

`x=5`

Explanation:

`3x + 6 = 21`

Following the correct rules in math:

Subtract both sides with "-6" to isolate 3x, making the equation looks like this:

`3x + 6 - 6 = 21 - 6`
`3x = 15`

Divide both sides by 3 to come up with x, making the equation:

`cancel((3x)/3)` = `cancel(21/3)`

Final answer is:

`x=5`

SHORTCUT METHOD:
This one does not follow the correct rules in math but this is very helpful for "limited time" exams.

`3x + 6 = 21`

Transfer +6 to other side of the equation, converting the sign to opposite one making +6 to -6

`3x = 21 - 6`

Subtract

`3x = 15`

Divide it by the number with `x`

`cancel((3x)/3) = cancel(15/3)`

Final answer

`x=5`