How do you solve 3x + 6 = 21?

1 Answer
Feb 29, 2016

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