Answer: 281.25 milligram
Step-by-step explanation:
Given
Milligrams of aspirin left after t hours is given by

for 

To solve the two sets of equations simultaneously, subtract one equation from the other to obtain
3x^5 + 2x^2 - 10x + 4 - (4x^4 + 6x^3 - 11) = 0
3x^5 - 4x^4 - 6x^3 + 2x^2 - 10x - 7 = 0
This is a polynomial of degree 5 to be solved for zeros.
A graphing calculator will yield 3 real zeros (verifiable by Descartes Rule of Signs).
<span>y = 2x + 20. The answer is A. Explanation: Vlad spends a known amount of time on his history homework (20). On top of it, he also spends an unknown amount of time on solving a number of math problems (x). Each problem takes two minutes to solve, so the amount of time that he spends solving math problems is 2*x or 2x. In total (y), Vlad spends 20 + 2x amount of time on his homework. So y = 2x + 20, where y is clearly greater or equal to 20 and x is greater or equal to 0.</span>