Question

If `-1/3x+7=4`, what is `1/3x+3`?

Answer 1

See a solution process below:

Explanation:

Step 1) Solve the equation for `x`:

`-1/3x + 7 = 4`

`-1/3x + 7 - color(red)(7) = 4 - color(red)(7)`

`-1/3x + 0 = -3`

`-1/3x = -3`

`color(red)(-3) xx -1/3x = color(red)(-3) xx -3`

`color(red)(-3)/-3x = 9`

`1x = 9`

`x = 9`

Step 2) Substitute `color(red)(9)` for `color(red)(x)` in the expression and then evaluate the expression:

`1/3color(red)(x) + 3` becomes:

`(1/3 xx color(red)(9)) + 3 =>`

`color(red)(9)/3 + 3 =>`

`3 + 3 =>`

`6`

Answer 2

`x=9`

`1/3x+3=6`

Explanation:

Solve the first equation for `x`.

`-1/3x+7=4`

Simplify `-1/3x` to `-x/3`.

`-x/3+7=4`

Subtract `7` from both sides.

`-x/3=4-7`

Simplify.

`-x/3=-3`

Multiply both sides by `3`.

`color(red)cancel(color(black)(3))^1xx(-x/color(red)cancel(color(black)(3))^1)=-3xx3`

Simplify.

`-x=-9`

Multiply both sides by `-1`.

`x=9`

Now substitute `9` for `x` in the second expression.

`1/3x+3`

Simplify `1/3x` to `x/3`.

`color(red)cancel(color(black)(9))^3/color(red)cancel(color(black)(3))^1+3`

Simplify.

`3+3=6`