there are 50 wildflowers per square inch in a triangular area of the field, so assume that the field is uniformly populated with wildflowers... this means that the rectangular area also has 50 wildflowers per square inch.

Calculate the number of square inches in the field and multiply that by 50, there are 12 inches in a foot so the conversion factor from feet to inches is 12/1:

3*(12/1)*5(12/1)*50

=36*60*50

=108,000 wildflowers