How to write this equation step by step?!

1-for what value of x is line a parallel to line b 2-for what value of x is line a parallel to line b

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

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.