To solve you can use inverse operations.
Here are the steps to find the answer:
1. Write out the equation: -6(x-2)+3x= -3(x+3) +21
2. Distribute both sides: -6x+12+3x= -3x-9+21
3. Simplify both sides: -3x+12=-3x+12
4. This equation is true for all values, or infinity, because the equation is the same on both sides
Let me know if you need further explanation. I hope this helps.