9+2x=18 if you can slove the prople

Not sure what the question is.
9+2x=18
Subtract 9 from each side then...
   2x=9
Divide each side by 2 and you'll have that x is
  
x=4.5

Not sure if I answered correctly.

Since 9 does not contain the variable to solve for, move it to the right-hand side of the equation by subtracting 9 from both sides.
2x=−9+18

Add −9 and 18 to get 9.
2x=9

Divide each term in the equation by 2.
x=9/2

Exact Form: 
9/2 

Decimal Form: 
4.5 

Mixed Number Form: 
4 1/2

T = S - 6n

Step-by-step explanation:

Let T be the temperature of the city after 'n' weeks, and let S be the starting temperature of the city.

If the temperature change is the same each week, the average change per week is given by:

The expression that describes temperature as a function of the number of weeks is: