Every letter a decimal digit, different letters for different digits:
BASE + BALL -------- GAMES
Which digit does each letter represent?
Assuming numbers can't start with 0,
If it is
There are in total three solutions (with unique numbers):
So apart from the solution in @f''s answer, we have
I found an answer by looking at the lowest numbers:
I set L to zero which means that there won't be a one to carry. This allows me to set E = S ("es", not "five"). Let's pick a number:
Let's pick a number for A. This also gives us M. Note that if 2*A is < 10, A has to be even because it equals 2B - 10. If instead 2*A >= 10, the one carries over and A has to be odd because 2B + 1 - 10 has to equal A.
Now I see that B + B has to equal 12. B = 6:
Using this method, I also found these results:
This method won't give every result because I'm assuming that L is always zero.