But you can look at it from another angle.
It consists of parallelogram and triangle.
Calculate the parallelogram first
S quadrilateral =50*30= 1500
Recalculate triangle
S triangle = base times height divided by 2.
=35* 15 divided by 2
=26.25 (I don't know if the calculation is correct)
Then the two add up again.
S triangle +S quadrilateral =1500+26.25 =1526.25.
(Note: * is a multiplication symbol)