What it is basically saying is that 9*8 is equal to 10*8 - 1*8 [Blank 1]. 10 times any number is a friendly number, it all ends with a 0. The question is saying that it is easier to think of a friendly number and subtracting from that. 10 eights - 9 eights is equal to 1 eight. So we take away 1*8=8 from 10*8=80, or in other words, 80-8 [Blank 2]= 9*8=72 [Blank 3].
