The sum of two numbers is 36. their difference is 4. determine the two unknown numbers.

So you know if a and b are the numbers that a+b=36 and a-b=4 so you can solve one I solved the second equation for a a=4+b and plugging that a value into equations gives you 4+b+b=36
This simplified to 4+2b=36
2b=32
B=16 so you know one number is 16 and you can plug it in to find a a-16=4 so a=20

Therefore the two numbers are 16 and 20

What mathematical statement is missing ? ? the answer is b