For this case, the first thing we must do is define a variable:
x: number of hours
y: number of trials
We write the equation that represents the problem:
y = (25/4) x
For 35 essays we have:
35 = (25/4) x
Clearing x:
x = 5.6 hours
Answer:
it will take him to grade 35 essays about:
x = 5.6 hours
the constant of this variation is:
25/4 essays / hour
