Set of linear graphs matching cards. 12 graphs with 12 equations in slope intercept form. 10 equations have positive slope and 2 are horizontal lines. For my classroom I typically copy on cardstock, print a set for each table group and then just have students match the pairs. A fast alternative is to pass out one card to each student and have them find their match.
Note: Duration options start at 30 minutes... it is unlikely this activity would last more than 10 if students are doing well graphing lines in slope-intercept form.