please help 15 points (picture)

Answer:
the first difference are all 20.
since the first differences of this relation are constant, it is a linear relation
Answer:
Linear because the account balance increases by a constant 20.
Step-by-step explanation:
→ The first difference is 20 for all values because :
20 - 0 = 20
40 - 20 = 20
60 - 40 = 20
80 - 60 = 20
100 - 80 = 20