To figure out the equation, start doing the computations for the first few bounces.
When there had been zero bounces (that is, when the ball hadn't been dropped yet), the height h was 200.
Since thirty percent of this height was lost on the first bounce, then the first bounce reached only seventy percent of the first height. What then was the height after x = 1 bounces?
After the second bounce, the ball reached only seventy percent of the height after the first bounce. What was the height h after x = 2 bounces?
And so forth, until you notice the pattern, and create the formula.