X - 3 = 7
add 3 to both sides
x - 3 + 3 = 7 + 3
x = 10
addition property of equality
im not sure but maybe look up how to calculate volume of a cone.. then go from there :D
ANSWER

EXPLANATION
The average velocity of the ball is the rateof displacement over the total time.
The height of the ball, in feet, after t seconds is given by the function:

At time t=1, the height of the ball is


At time t=6, the height of the ball is



The average velocity




Hope this will help you. It is a little hard to explain.
Just count, its really simple...its hard to explain using a keyboard tho...sorry i wasnt much help