Answer:

Explanation:
If Maria has written already "z" words of her 1000 words essay, so the number of words she has left to do is "1000-z". Then the amount of time "T" that is left for her, is the quotient between 1000-z over 63 words/min (her writing rate).
We can then write that the time (T) it will take her to write the rest of the essay is:

where we express the resultant function in slope-intercept form.