Chris is c yrs old .tom is 5 years old younger than twice chris's age .write an expression to represent tom's age?

Iam so stuck. what is the worked out answer for this question?

Determine whether the quadrilateral below is a parallelogram. justify/explain your answer (this means back it up! give specific information that supports your decision. writing just "yes" or "no" will result in no credit.)

Can someone show me step by step how to do this?