xvxvxv

$16x-4-7x$

$9x-4$

In addition to what Dragonlance say 

the formula is $v^2 = vi^2 + 2gd$

where vi is the initial velocity and its zero because its start from rest 

11 + 13 + 3! = 30  

Perfect post. 

Thank you Melody 

This is the rest of the solution 

Thank you melody :) 

You need another equation to solve this 

a-6=8-9-a

move "a"  to the left side with opposite sign and  6 to the right side with opposite sign 

a+a=8-9+6

2a=5

a=5/2

a=2.5

There is no solution. 

multiplying the angle ( in radian ) by the radius 

for example, the circumference of the circle = 2*pi*r 

where (2*pi) is the angle and ( r ) is the radius.