They are collinear points and are called planes.
Collect like terms
(2x-x) + (9+3)
Simplify
x+12
<span>0.48333333333 or if u round it off it would be 0.48</span>
For this case we have the following equation:

We must clear the value of the variable "x" as a function of r, s and t:
If we multiply by "r" on both sides of the equation we have:

If we subtract "t" on both sides of the equation we have:

If we divide by "2" on both sides of the equation we have:

Thus, the value of the variable "x" is:

Answer:

<span>6.75 inches....................
</span>