The best way to solve this is to break the shape up into areas you know how to solve.
Lets divide this into the big rectangle being separated from the smaller rectangle at the bottom.
To find the height of the big rectangle, subtract one y-coord of 30 from the other y-coord 80.
80-30=50
To find the length of the big rectangle, subtract one x-coord of 10 from the other x-coord of 100.
100-10= 90
Multiply these to get the area of the big rectangle:
90 x 50 = 4500 units squared
Next, find the smaller recatngle’s area by repeating the previous steps:
Height: 30-10 = 20
Length: 70-40 = 30
Now find the area:
20 x 30 = 600 units squared
Finally, add both of these areas up to find the total area for the original shape:
4500 + 600 = 5100 units squared
Hope this helped!