PLEASE help

NOT positive about this....

100 thru 999 is 900 3-digit numbers

there are 180 multiples of 5

there are 128 multiples of 7

there are 26 multiples of 35  (which must be subtraced to avoid double counting)

900 - (180+128-26) = 618       Corrected after input from Rom....Thanx ! 

Good job, EP! I'll just go over the formula. These steps are called PRINCIPLE OF INCLUSION AND EXCLUSION, and it comes up in many problems. Just what EP said, overcounts are there, and you have to remove them!