These solutions relate to puzzles found in Issue 04 of the magazine.
Odd sums
The sum of the first n odd numbers is n2 (this can be proved by induction). This means that:
sum of the first n odd numberssum of the next n odd numbers=n2(2n)2−n2=n23n2=13
Odd squares
1 and 9 are the only two square numbers whose digits are all odd.
Two lines
The co-ordinates will be (1,gradient+intercept).