After the first three days, the sample size will be half of the initial; therefore, 400g/2= 200g. However, it is asking how long will it take to decay to 100g, so we will take 200g/2= 100g, which will take another three days. It will take 2 half-lives, which will encompass 6 days.
10.20*8= 81.60
10.20*.5= 5.10
add
81.60+5.10= 86.70
ANSWER: Peter pays $86.70 for the carpet
It’s c since the line goes down 5 and the y intercept is 3 so it would be y=-5x+3