The steps below show the incomplete solution to find the value of x for the equation
6x − 2x − 5 = −6 + 21:

step 1: 6x − 2x − 5 = −6 + 21
step 2: 6x − 2x − 5 = 15
step 3: 4x − 5 = 15

which of these is most likely the next step?

Step 1: 6x - 2x - 5 = -6 + 21 
Step 2: 6x - 2x - 5 = 15 
Step 3: 4x - 5 = 15 

The next step would be to add 5 to both sides of the equation. 
so Step 3: 4x - 5 = 15 add 5 to both sides would make 
Step 4: 4x = 20 
 
So after the next step you would have 4x = 20 

Hope this helps! :) 

    

If you make you answer for clear i can answer it : )