Answer:
Eric's expression is :

and Andrea's is :

In Eric's expression, 20 represents the initial amount of substance with which he has started the experiment.
is the amount of substance left after each time period (in this case, each week).The variable w in this case represents the number of weeks.
Andrea's expression can be written as :

The one outside of parentheses represents the initial amount of the substance. The one inside of parentheses represents 100% of the original amount of the substance. 0.5 represents the 50% of the substance that is lost each time period. The variable w in this case represents the number of weeks.
- Here, both the triangles have equal sides.
- So, the two triangles are related by SSS.
- If all the sides of a triangle are equal to all the sides of another triangle, so the triangles are congruent to each other.
<u>Answer</u><u>:</u>
<u>SSS,</u><u> </u><u>congruent.</u>
Hope you could get an idea from here.
Doubt clarification - use comment section.