Chapter 4.6, Problem 48MS

Here we celebrate the power of algebra as a powerful way of finding unknown quantities by naming them, of expressing infinitely many relationships and connections clearly and succinctly, and of uncovering pattern and structure.

Is x big enough? A triangle drawn on the sphere has angles measuring 80,90 and x dcgrees. If x satisfies the equation $x^2-30x+200=0,findx.$

(There’s only one value for x that works. What is it and why?)