Pleaseee help me I’m stuck

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

How do i do this activity, is appreciated

Eric has challenged himself to walk 24,000 steps in 4 days. if eric walks the same number of steps each day, which function represents the number of steps eric still needs to walk to reach his goal with respect to the number of days since he started his challenge? a. y = 8,000x − 24,000 b. y = -8,000x + 24,000 c. y = 6,000x − 24,000 d. y = -6,000x + 24,000