Question

How do you solve `5d - 6= 3d + 9`?

Answer 1

Subtract `3d` from both sides then add `6` to both sides,
then divide by the coefficient of the variable to get `d=7 1/2`

Explanation:

Given
`color(white)("XXX")5d-6=3d+9`

By subtracting `3d` from both sides we can remove any term containing a variable from the right side:
`color(white)("XXX")5d-6color(blue)(-3d)=3d+9color(blue)(-3d)`

`color(white)("XXX")2d-6=9`
Now, if we add `6` to both sides we can remove any constant term from the left side:
`color(white)("XXX")2d-6color(blue)(+6)=9color(blue)(+6)`

`color(white)("XXX")2d=15`

Finally dividing both sides by `2` reduces the left side to a unit variable:
`color(white)("XXX")2dcolor(blue)(div 2)=15color(blue)(div 2)`

`color(white)("XXX")d=7 1/2`

Answer 2

`5d-3d=6+9`
`2d=15`
`d=15/2`
`d=7.5`

Answer 3

`7.5`

Explanation:

`5d-6=3d+9`
First, we will remove `3d` from both sides.
`5d-6(-3d) = 3d+9(-3d)`
The `-3d` in the brackets represent what we will remove.
That will equal `2d-6=9`
`9+6=15`
`15=2d`
`1d=15/2=7.5`
Solved!