This is a "dominos" like activity where students will choose a card to start on, set up and solve the proportion problem, find the answer on another card and then solve the problem on the same card that had their answer on it.
They continue this process until they have lined up all their cards like dominoes. This activity could also easily be completed using stations or a scavenger hunt type task depending on the needs of your classroom.
I usually have pairs complete this activity. Depending