Use the linear combination method to solve this system of equations. what is the value of x?
3x + 7y = 31
-3x - 2y =-1

a) -6
b) -3 2/3
c) 3 2/3
d) 6

Aball is thrown from a height of 139 feet with an initial downward velocity of 15 ft/s. the ball's height h (in feet) after t seconds is given by the following. h=139-15t-16t^2 how long after the ball is thrown does it hit the ground? round your answer(s) to the nearest hundredth. (if there is more than one answer, use the "or" button.) t =