Hi Amy!
Area of parallelogram equals Base X Height.
g(x)=2 is the line y=2.
The line parallel to the y-axis passing through (5,10) is x=5.
Area equals 2 (height) times 5 (base). Area equals 10. A=bh. If you draw it out, it makes sense.
Please let me know if you read this. Most don't. We all respond because we can, but no one acknowledges.