Ann picks a 4 digit number . the first digit is not a zero .the 4 digit number is a multiple of 5. how many different 4 digit numbers could she pick?

_  _  _  _
since it has to be a four digit number and the restrictions are only two substitue the first digit with 1 
1  _  _  _
then substitue the last one with 1 because there is only one multiple of 5 that is a single digit

1  _  _  1

then substitue the second gap with 8 because 0-9 are ten numbers and since you already used 2 numbers 10-2 is 8
1 8 _ 1

then substitue the last gap with 7 because you already used three numbers

1 8 7 1

then multiply all of them and you get 56

If you make it a little more clear i can answer it