90
It is: 80
To be a multiple of 4, 10 and 20 the number must be a multiple of their lowest common multiple. lcm(4, 10, 20) = 20 What is required is a multiple of 20 between 61 and 107. The numbers 80 and 100 both satisfy the problem of being between 61 and 107 and being a multiple of 4, 10 and 20.
All numbers that are multiples of all 2, 8 & 10 are multiples of their lowest common multiple which is 40.The multiples of 40 are 40, 80, 120, 160, ... of which only 80 is between 61 and 107.
It is: 80
90
90
80
The number is 90.
98
80 adn 100
There is only one. It is 70.