2.434 to 3 sigfigs = 2.43 .
The toy rocket hits the ground when h(t) = 0.
So, h(t) = 0 = -9t^2 + 81.
Solving the equation,
-9t^2 = -81
Dividing by -9
t^2 = 9
Taking the square root.
t = 3
The answer is 3 seconds.
3/4 (x-12)=12
3/4x - 9= 12
+9 +9
3/4x=21
*3/4 *3/4
x= 15 3/4
and
3/4y-12=12
+12 +12
3/4y = 24
*3/4 *3/4
y= 18