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

Question

20939 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-02-29T06:24:44

#x=5#

#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#