I Spy with Regan

I played the maths game called "I Spy - Addition", it is a card game. When I add 9 plus 3 I calculate a number to 10 first (9 plus 1) and then I add on the difference of 2 to get the correct answer of 12. My strategy was to make it harder for Paula to find the cards so I added 2 cards together that were placed diagonally on the table.