As a decimal 4/15 = 0.2666667
As a decimal 3/10 = 0.3 [talk about close]
3/10 is bigger.
You could take an average to find something between 4/15 and 3/10
1/2(4/15 + 2/10)
1/2(8/30 + 6/30)
1/2(14/30)
1/2(7/15)
7/30 is between the two given numbers..
Let's call he width of the notebook w and the length l
w*l=80
2(w+l)=36
w+l=18
w=18-l
(18-l)*l=80
-l^2+18*l-80=0
l=8 or 10
Therefore, the notebook is 8 by 10 inches
Given the line, we have points (0,4),(1,3), (2,2), (3,1) and (4,0)
Hence, y= 4-x
You're using the commutative property when you swap the order of factors in a multiplication:

and you use the associative property when you regroup the products of more than 2 factors in a different way:

So, you're constantly alternating between associative and commutative. Try to see which property you're using in the first step, and then keep alternating between the two!