The current price of bulk organic sugar is $6 per pound, which is 20% more than it used to retail for last year. What was the previous price?

      Statement                                                    Reason

1. Parallelogram ABCD                                      1. Given

2. Side AD is parallel to side BC                      2. Definition of a parallelogram

3. Side AB is a transversal of AD and BC        3. Definition of a transversal

4. ∠A and ∠B are same side interior angles   4. Definition of SSIA

5. ∠A and ∠B are supplementary                    5. SSIA between parallel lines

6. Side CD is a transversal of AD and BC        6. Definition of a transversal

7. ∠C and ∠D are same side interior angles   7. Definition of SSIA

8. ∠C and ∠D are supplementary                    8. Same Side Interior Angles,

                                                                              SSIA, theorem

Step-by-step explanation:

Given that the quadrilateral ABCD is a parallelogram, we have;

Side AD is parallel to side BC, and side AB is a common transversal to AD and BC

∠A and ∠B are same side interior angles, SSIA, formed between parallel lines, therefore, according to Same Side Interior Angles theorem, we have;

∠A and ∠B are supplementary angles and therefore, ∠A + ∠B = 180°

Similarly, the angles ∠C and ∠D formed by the transversal CD and the parallel sides AD and BC are same side interior angles

∴ ∠C and ∠D are supplementary angles and ∠∠C + ∠D = 180°