The key to most of these puzzles is to recognize that they are not equations and that they have very little to do with mathematics other than simple arithmetic.
Take the first so called “equation”; 7+3 does not equal 41021, but 7+3 does equal 10 and note that 10 appears within the string 41021.
Does this result hold for any of the other “equations”? Yes it does. The result of adding the two numbers on the left hand side is embedded within the string on the right hand side for all the “equations”.
Back to the first “equation”: 7-3 = 4, the difference between the left side numbers appears as first number in the right hand string. This holds true for all the equations.
We are almost home: the product of the left hand numbers appears at the end of the right hand string in every case.
The right hand string is constructed by concatenating the difference, the sum and the product of the two left hand numbers.
Test on the final equation.
17-8 = 9, 17+ 8 = 25, 17*8 = 136 giving us the string 925136