Question

How many numbers are equal to the sum of two odd one digit numbers

Answer 1

Assuming odd one digit numbers are to be positive non-zero numbers, namely 1,3,5,7,9.

The possible sums are
1+1=2
1+3=3+1=4
1+5=5+1=3+3=6
1+7=7+1=3+5=5+3=8
1+9=9+1=3+7=7+3=5+5=10
3+9=9+3=5+7=7+5=12
5+9=9+5=7+7=14
7+9=9+7=16
9+9=18

I count 9 numbers.

Zero is considered even.
If one digit numbers include negative numbers, proceed similarly as above.

Answer 2

The answer is NINE.

1+3=4
1+5=6
1+7=3+5=8
1+9=3+7=5+5=10
3+9=5+7=12
5+9=7+7=14
7+9=16
9+9=18
1+1=2
3+3=9

Hope it Helps.
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