Question

How do you solve `2x + 4x + 3x=21`?

Answer 1

I found `7/3`

Explanation:

You can add together all the terms on the left because they have the same litteral part and get:
`9x=21`
you can now transfer the `9` to the right but dividing as:
`x=21/9`
This is because in your Equation the left has always to be equal to the right. If you decide to get rid of the `9` on the left (dividing by `9`) you must do the same on the right:
`(9x)/(color(red)(9))=21/(color(red)(9))`
`(cancel(9)x)/(cancel(9))=21/(color(red)(9))`
now you can divide both by `3`:
`x=(21/3)/(9/3)=7/3`