79.90*0.8= 63.92
Answer
63.92
Answer:
Part 1) 
Par 2) 
Part 3) 
Step-by-step explanation:
step 1
Find the 
we have

Remember that

therefore

step 2
Find the 
we know that

we have

substitute




square root both sides

we have that
---> given problem
so

step 3
Find the 
we know that

we have


substitute

Simplify
