Please help me explain step by step. I am very lost in counting.how many positive integers less than 1000

a) are divisible by 7 but not by 11?

b) are divisible by either 7 or 11?

c) are divisible by exactly one of 7 or 11?

d) are divisible by neither 7 nor 11?

e) have distinct digits?

f) have distinct digits and are even?