how many integers from 20 to 150 , inclusive , are divisible by 3 but not divisible by 7 ?
"we should find # of integers divisible by 3 but not by 3 * 7 = 21 . # of multiples of 21 in the range from 20 to 150 , inclusive is ( 147 - 21 ) / 21 + 1 = 7 ; 44 - 7 = 37 . answer : a ."
divide(150, const_10)