All you have to do is solve for x. See the following steps below.
Step 1. Subtract

from both sides

Step 2. Simplify

to

Answer:
n= 1
Step-by-step explanation:
7+3(n-1)
10(n-1)
10n=10
n=10/10
n=1
I think that your answer would be the second option. R= m-200/d.Hope this helps! Tell me if this is right if you don't mind.