Simultaneous equation help

I have to determine the values of a and b in this equation. I'm told to use simultaneous equations. But I can't find my notes on them, although I'm not sure that would help me anyways. The log bit also adds to the confusion:confused:

The equation is:

log M = av + b

Now I know M, it is 45,000 for substance O, and is 17,200 for substance Y.

I also know v, it is 0.000258 for substance O, and is 0.000916 for substance Y.

If you could use the substitution method, that would be great as that is the one I found easier in class. Thank you. Please say if you need any more information.