Mari and Jack each bought a sofa from a furniture store. Mari’s sofa cost $600. She paid $200 when she bought it and pays $20 per month. Jack’s sofa cost $810. He paid $140 when he bought it and pays $50 per month. After how many months will Mari and Jack each
owe the same amount on their sofas?
a)2
b)4
c)5
d)9