If I were solving this equation, I would put x^2-20x+(100)=(10). Since this is in standard form, you could change this into vertex form by making the equation y=(x-10)^2 -10.
I think they’re perpendicular lines
The decimal is about 1.1 and you can’t simplify it
525 divide 35 = 1515 times 1.38= 20.70 dollars