Answer:
C) -3x=-3
Step-by-step explanation:
When you subtract the 3x-y=7 from 6x-y=10, you will receive the following equation:
3x-6x-y-(-y)=7-10
-3x-y+y=-3
-3x=-3
As we can see, this equation matches the one in option C, meaning that it's our answer!