What is the Square root of 39

Apatient is given 50 mg dose of medicine the medicines effectiveness decreases every hour at a constant rate of 40% what is the exponential decay function that models this scenario how much medicine will be left in the patients system after 2 hours

Which is the equation of an ellipse with directrices at x = ±4 and foci at (2, 0) and (−2, 0)?

When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer