That's true but generally that applies to purely abstract mathematics. If the mathematics is truly abstract, no form of IP anywhere would protect it. That has always been (rightfully IMO) the realm of scientific publications.

Otherwise it's straightforward to say that the mathematics is being applied to achieve a practical goal via execution on a computer. (You'll see the term non-transitory computer-readable media" a lot in claims.) You now have a method and system. Now, caselaw frequently changes things, like the "Alice" decision in the US made it much harder to just patent things done "on a computer" but the underlying principle holds.

I'd also guess if your approach makes something faster or cheaper, it should be possible to show it is non-abstract, because resources like time and costs are not abstract quantities.

Standard disclaimer: I'm not a lawyer! I've just worked with patents extensively.