The tenths place is right after the decimal point. So, 3160.9903 can be 3160.9.
A sequence of operations that will get you to the solution is ...
... d. multiply each side by-5, add 25 to each side
_____
That is not the only correct sequence of operations. However the other ones listed here are incorrect ways to get to x = -10.
You can do whatever multiplication and addition you like to each side of the equation, but if those operations are poorly chosen, they will make finding the solution more difficult.
