Amahogany desk with a cash price of $810 is offered on the installment plan at $50 down and $58 per month for 15 months. what is the total cost of the desk?

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.