Find the error in this solution then solve correctly.

Question

9x +18 + 3x = 1

9x +18 = -2

9x = -20

x = -20/9

Answer 1

The error is going from step 1 to step 2. 3x is not the same as 3. The given solution is showing 1 - 3 instead of 1 - 3x. So the correct solution would be:

 

9x + 3x + 18 = 1 (Rearranged to put like terms together)

12x + 18 = 1

12x = -17

x = -17/12

Answer 2

Assuming the first line is correct, start with:

 

9x +18 + 3x = 1

 

Combine like terms to get

 

12x = -17

 

Solve for x and get

 

x = -17/12

 

The error was in writing 9x + 18 = -2, since from the first line you can obtain 9x + 18 = 1 - 3x.