4. Peter's weight decreases from 80kg to 64kg.
Calculate the percentage decrease in Peter's weight.

20% decrease

Step-by-step explanation:

First, let's find the net decrease: Peter started at 80kg and his weight is now 64kg, which is a 16kg decrease. Next, we need to find what percentage of 80kg 16kg represents. First, let's find what part of 80 is 16:

16/80 = 1/5

To convert this to a percent, we need to find an equivalent fraction to 1/5 with a denominator of 100. To do this, we can multiply the numerator and denominator of 1/5 by 20, giving us 20/100, or 20%.

2

c. (3,2,6) is the answer.