The three scores are 86, 74, and an unknown score x. The average (i.e. the sum divided by how many there are) is 80, so we have

Multiply both sides by 3 and you get

Subtract 160 from both sides to get

Note: you could solve this exercise very quickly if you notice that the two numbers, 86 and 74, are symmetrical with respect to 80, which is the average. So, the third number must be the average.
Subtracting the weight of the smaller brick from the larger gives us the weight difference:
4 3/8 lb - 2 1/3 lb. The two denominators are 8 and 3 respectively, resulting in an LCD of 24. Thus, our problem becomes:
4 9/24 - 2 8/24, which equals 2 1/24 lb. The weight difference is 2 1/24 lb.
Answer:

Step-by-step explanation:
Given

Required
How it'd be displayed on a calculator
Standard calculators, today are built to always convert huge numbers or extremely small number to scientific notations;
This was done to allow the calculator fit each values on its screen
is such a big number that it'll require the calculator to display it using scientific notations;
So, basically we have to convert
to scientific notaton;
This is achieved by replacing
with 
So,
is equivalent to 
I think it is..................