In a row, Brian is standing $150\text{th}$ from the left and $275\text{th}$ from the right. How many people are there in the row?

To find the total number of people in a row when the position of a single person is given from both ends, use the standard ranking formula:
$$\text{Total number of people}=\text{Position from Left}+\text{Position from Right}-1$$

$$\text{Total}=150+275-1$$

$$\text{Total}=425-1=424$$