The answers given are more specific, but I wanted to give you a more general answer. When you have multiple lines like this, what they are asking you to do is to think about the shape that it makes. For any particular part of the graph, there will only be two curves that matter. However, to find out which two of the three curves are important, you have to plot them, and then solve for the specific point that it intersects.
You can see the plot here:
Notice that it makes a semi-triangular shape. Therefore, the goal is to find the area of the triangle. The top function for the whole thing is y = 3. The bottom function switches from the linear function to the square root function somewhere in the area of x = 1 (just from looking at the graph). To know exactly, you need to solve for where these are both equal to each other.
Then, you find the area between the two functions (the y = 3 and the linear function) until the switchover, and then, after the switchover happens, you find the area between the other two functions (y = 3 and the square root function).