The number is 200 .
10 is 5% of 200
First add like terms in this case 1+7=8. Then then divide. 2x/8= 4. X=4
The expression of the height is

the index "n" is the numbers of times that the ball is down, to n=1 the height is 8 inches, to n=2 the height is 4 inches.
An when n=5, the height is

the anwers is 0.5 inches