Everything is supposed to equal 180

Solve the system of equations. y= 2x y= x^2 - 15

Which of the expressions (on the photo document i inserted) together represent all solutions to the following equation? 8cos(12x)+4=-4 *the answer should be in degrees.* > i would like for someone to explain the process to find the solutions for this.

Aquadratic equation in standard from is written ax^2= bx+c, where a,b and c are real numbers and a is not zero?