Chapter 1 - Section 1.7 - Modeling with Equations - 1.7 Exercises - Page 80: 91

$4.55ft$

We have a simple right angle triangle, with one leg $3ft$. And the sum of hypotenuse and second leg is $10ft$. Let hypotenuse be $x$, so the second leg will be $(x-10)ft$ Using Pythagoras theorem, we can write: $3^2+(10-x)^2=x^2$ $9+100-20x+x^2=x^2$ $20x=109$ $x=5.45$ So, the height of this break is $10-5.45=4.55ft$