Number encoding puzzle

An "ancient" writing system for numbers was discovered:

How would the number 75 be represented with this code? (Two symbols)

I think I made it too hard, here are some hints:

• Is the use of graph paper and the alignment of the symbol w.r.t. the paper relevant to the question? Sep 24, 2023 at 1:37
• @Someone I would assume so; I tried using the area of each shape and putting it in as the different digits, but that doesn't seem to work. Maybe it's the length of each line (the X symbol led me to that conclusion). Sep 24, 2023 at 2:28
• The problem with that is that it would be very square-rooty. Sep 24, 2023 at 20:49
• Can you give more examples of arithmetic equations as hints? Sep 25, 2023 at 14:42

I think 75 is

The number system is

hexadecimal (75 = 4B), with 0 being X, F being the square, and 1 being the down-facing triangle. To get a missing digit, take the square and visually subtract the "opposite" number symbol from it. E.g. the shape below is E because 1 (the triangle) was cut out

• You are correct! Sep 25, 2023 at 16:54