algebra
posted by lisa .
The number of tickets sold each day for upcoming perfomance of Handel's Messiah is given by N(x)=0.6x^2+15.6x+12, where x is the number of days since the concert was first announced. When will daily ticket sales peak and how many tickets will be sold that day?

Do you know Calculus?
If so, find the derivative, set it equal to zero and solve for x
evaluate f(x) for the given x you found
if not
complete the square, sort of messy with these numbers.