10 / 2 = 5 snails each
10 = 8 (snails in one) + 2 (snails in the other)
3 + 7 = 10
4 + 6 = 10
5 + 5 = 10
If you go from 5 snails per tank and you want to add, you go up with one number and down with the other each time you write the problem a different way, but the sum cannot be over 10. If you multiply, then you know you have 10 snails and only two tanks. Doing mental math, you should be able to find out that 2 times 5 is 10. If you want to divide, you can basically do the opposite, which would be 10 divided by 2, and the answer is 5.
Hope I was able to help! (and sorry if it may be a little confusing)
