I wanted to use this as a stumper "__(M + M) = 1939"?

I easily had over 50 of these, but they were a bit repetitive after a while, which is why I added the years to the equations. If this is popular, then, as with all good movies and many bad ones, there will be a sequel.

The Answer Key will be up soon -- as soon as I find it. Yes, a couple of them are stumping me now and I wrote the thing!