Answer:
y = 
Step-by-step explanation:
to get the hypotenuse:
use the Pythagorean theorem:
a² + b² = c²
where a = 19, b = 8.2 c = y
plugin values:
19² + 8.2² = y²
y = 
We know that the 15% of missing pencils is equal to 9
we can use this formula
9/x = 15/100
Then cross multiply
15x = 900
x = 60
There were orignally 60 pencils