Is x = 8 a solution to the equation 16 - x/4 = 12?

The graph of y = ax^2 + bx + c is a parabola that opens up and has a vertex at (0, 5). what is the solution set of the related equation 0 = ax%2 + bx + c?

How do you solve a question like this?

An initial investment of $100 is now valued at $150. the annual interest rate is 5%, compounded continuously. the equation 100e0.05t = 150 represents the situation, where t is the number of years the money has been invested. about how long has the money been invested? use your calculator and round to the nearest whole number. years