HELP PLEASE! In exercises 5-10 determine whether the graph represents a linear or nonlinear fuction. explain (just short and to the point)

If you need an equation, it would be y=2x+8, y would be how long it grew, x being weeks.if you need how long he was asleep, it would be 4 weeks if he started with no beard, the equation would be x=8÷2if he did have a beard before hand, the equation would be 2w+x=8

The solution to the system of equations (-2,2)