The workers collected 30,000 gallons of milk and pumped 2,880 gallons/hour for 4 hours, which means they pumped a total of 2,880 * 4 = 11,520 gallons of milk into the milk tanker.
After pumping, the remaining milk in the storage tank is 30,000 - 11,520 = 18,480 gallons.
For the next x hours, the workers added more milk into the storage tank at a rate of 1,500 gallons per hour, so they added a total of 1,500 * x gallons of milk.
The total amount of milk left in the storage tank is the remaining milk after pumping plus the milk added in the next x hours: 18,480 + 1,500 * x.
We are given that the total amount of milk left in the storage tank is 28,980 gallons, so we can write: 18,480 + 1,500 * x = 28,980.
Simplifying the equation, we get: 1,500 * x = 10,500.
Dividing both sides by 1,500, we get: x = 7.
The value of x is 7.
#### 7
The answer is: 7
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
This morning, farmer Rita's workers collected 30,000 gallons of milk and chilled it in a storage tank. They then spent the next 4 hours pumping milk at a rate of 2,880 gallons/hour from the storage tank into a milk tanker. For the next x hours, the workers added more milk into the storage tank, at a rate of 1,500 gallons per hour. How many gallons of milk were left in the storage tank?
If we know the answer to the above question is 28980, what is the value of unknown variable x?

### Answer:
