Please help I need to bring my math grade up !

Julius sold five times as many computers as sam sold last year. in total, they sold 78 computers. how many computers did julius sell?

Ihave trouble finding the nth term of a linear sequence

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.