Harold kept x marbles, so he shared 100 - x marbles among his 5 friends.
To find out how many marbles each friend got, we divide the total number of marbles shared by the number of friends: (100 - x) / 5.
We are given that each friend got 16 marbles, so we can write: (100 - x) / 5 = 16.
Multiplying both sides by 5, we get: 100 - x = 80.
Subtracting 100 from both sides, we get: -x = -20.
Dividing both sides by -1, we get: x = 20.
The value of x is 20.
#### 20
The answer is: 20
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Harold had 100 marbles. He kept x marbles and shared the rest evenly among his 5 friends. How many marbles did each friend get?
If we know the answer to the above question is 16, what is the value of unknown variable x?

### Answer:
