85 had a white hand bag; 75 had black shoes; 60 carried an umbrella; 90 wore a ring;
How many ladies must have had all four items?
Answer: 10
Divide by 3. All the ladies had three items. The remainder shows the number of ladies who had 4.
85756090______310 / 3 = 100 + 10 remainder
Source: https://riddles.com/3529