I think the problem is
2X+20=400
You just have to answer I think X and X equals that two numbers I’m not 100% sure but I’m trying to help
I have no idea I’m answering this because I need to ask more questions
Answer: Apply the Sum/Difference Rule
d/dx(7x)-d/dx(8)
d/dx(7x)=7
d/dx(8)=0
7-0=7
Step-by-step explanation: The answer is 7