[__s]

It becomes much easier once you factor the number, rather than trying to narrow in on the answer

Light spoiler: gurer vf n fbyhgvba juvpu qbrf abg hfr bar uhaqerq

[gowld]

That's true if the solution is a product, not a sum.

[BizarroLand]

Start with the product solutions, and if nothing seems pliable, start backwards and work with the sum results.

For the hard one, 612 is not an easy number to find, but basic math shows that 6+1+2=9 so the number is divisible by 3 (and I won't go any farther to prevent spoiling it) Finding a system by which you create the situations that allow the operands and factors to be discovered while also flexing your basic math skills is the fun of the game.

[__s]

re 612, gjryir unf znal snpgbef fb fvk gvzrf uhaqerq znxrf sbe n avpr erznvavat qvfgnapr

[BizarroLand]

Fvk Uhaqerq nyfb unf znal plcuref ohg fbyivat jurer gb trg gur guerr sebz vf gur ovttrfg pyhr