This is a one-step equation, which means that it will only take 1 step to isolate x. That step is the inverse of the operation inn the equation. The operation in the equation is division, so you'd multiply both sides of the equation by 5.
x/5 = 25
*5 *5
x = 125
That undoes what you did to x and gives you your final answer!
The surface area of a sphere is where r is the radius; The circumference is so that using this value we can evaluate the surface area of 1 ball as: For 100 ball you get:
where r is the radius;
so that 
using this value we can evaluate the surface area of 1 ball as:
