Answer:
0.6 books
Step-by-step explanation:
Divide 9 by 15 to get 0.6 books a month
a21 = -61
(subtract to eliminate a₁)
9 = -3d
d = -3
-19 = a₁ + (6)(-3)
-1 = a
a21 = -1 + (21 - 1)(-3)
= -61
they will pay a lot my guy
6+6+6+6