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)