Question

If a and b are odd numbers, is it closed under addition and multiplication? Why or why not?

Answer 1

try it with generic odd numbers. they look like
\[2k+1, 2j+1\]

Answer 2

try adding and multiplying and see if you get even or odd or you don't know. you can also try it with specific odd numbers to guess what the answer should be. for example
\[3+5=...\]

Answer 3

It might help to rephrase the question: The question is asking: "Does an odd plus an odd = an odd ALWAYS? " and "Does an odd times an odd = an odd ALWAYS?"