[classicman]

I learned a way to remember them that was unique - can't write it out here, but it makes them so easy... searching for a link - not happening. It was something about subtract one from the number and then add whatever was necessary to make nine... 9x8 - one less than 8 =7 add 2 to equal nine. Hence the answer is 72. I dunno after looking at the link I prefer Jinx's method.