If the region east of plain B has an area of 200 square miles, and the region east of plain A is 50 square miles less, then the region east of plain A has an area of 200 - 50 = 150 square miles.
The total area of both plains is the sum of the area of plain A and the area of plain B, so it is 150 + 200 = 350 square miles.
#### 350
The answer is: 350
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If the region east of plain A is 50 square miles less than the region east of plain B, and plain B has an area of 200 square miles, what is the total area of both plains?

### Answer:
