Well, if you subtract by adding, you count in your head how many numbers are between 36 and 71. For example.. 80-50, there are 30 numbers in between 50 and 80 and 80-50=30.. If its easier.. try taking away one number in your equation and making them even.. like 70 - 35 and counting up by 5's.. so count 5, 10, 15, 20 until you get up to your number and just add 2 to your result for the 2 you took away (:
