Mr. Beck visited Mr. Grimes today and discovered he had a My Little Pony collection. Mr. Beck found 4 ponies on the mantle and Mr. Grimes said he is buying 2 more each day. Mr. Beck left the house and decided to start
his own collection. Each day he buys more than he did on the previous day. After a while, Mrs. Beck became
annoyed with the ponies, made him stop buying them, and started getting rid of them. It took her the same
number of days to dispose of them as it took to collect them.

Write an equation to represent Mr. Grimes’ pony collection. Be sure to indicate that number of days
is your independent variable and total amount of ponies is your dependent variable.