hukumen.py

import sys

def main(eq):
    eq = eq.replace("=", "==")

    for i in range(0, 10):
        try:
            if eval(eq.replace("X", str(i))):
                print("X=%d" % i)
                return
        except SyntaxError:
            pass
    print("X=none")


main(sys.argv[1])

test_hukumen.sh

#!/bin/bash

set -eu

echo "Input : 123+4X6=X79, Answer : X=5"
python hukumen.py "123+4X6=X79"

echo "Input : XX22+89=X2XX, Answer : X=1"
python hukumen.py "XX22+89=X2XX"

echo "Input : 12X+4X6=X79, Answer : X=none"
python hukumen.py "12X+4X6=X79"

echo "Done!"