20
Step-by-step explanation:
Step 1:
Let the number be 50 and to find 40% of 50 is given interms of expression as follows
To express the percentage the following strategy is used
Eg: 40% = 
∴ To express 40% of 50 is

Step 2:
On simplification the above expression we could get

= 20
Ft. Lauderdale is a city that stretches several miles, and Haiti
is a whole country, that's many miles wide and many miles high.
In order to nail down a reliable answer, you'd really need to specify
one point in Ft. Lauderdale and one point in Haiti.
If you start at the northwest end of Runway-13 at Ft. Lauderdale
Executive Airport, and take the shortest possible route to the east
end of Runway-28 at the Aeroport International de Port au Prince
at Haiti's capital city, you'd have to travel 727.57 miles.
But if you start in Ft. Lauderdale at the intersection of Griffin Rd
and Ravenswood Rd, and take the shortest possible route to the
Dispensaire de Bord-de-Mer hospital on Haiti's north coast, you'd
only have to travel 613.63 miles.
You really need to say WHERE in Ft. Lauderdale and WHERE in Haiti.
The answer to the problem is A
y=4x+40
x represents the number of minutes
y is the total
40 because he already graded 40 papers, and 4x because that's how many phred grades times the number of minutes