My math teachers had no problem with '42 = x' vs 'x = 42' as long as the steps made sense to get there. In fact they'd probably comment that there was no need to go with 'x = 42' if I obviously took a circuitous route simply to end up with x on the left side of the equation, as that would have demonstrated a lack of internalizing some of the base ideas of algebra and it's approach of equation symmetry.

You should distinguish the meaning of = in mathematical and meta-mathematical statements. “42y = yx, therefore 42 = x” is fine; but “let 42 = x” is not.

Some older C coding styles recommend that order because before compilers added warnings, “if (17 = variable)” resulted in a diagnostic, while “if (variable = 17)” would not. Nowadays, I think most programmers prefer putting the fastest-changing expression first.

Yeah that is due to clever C semantics that that should never had allowed for anything other than boolean expressions in conditionals like proper grown languages.