Achess club has 500 members but is losing 30 members each year. a computer club has 150 members and is gaining 20 members per year. write and solve an equation to find the number of years it will take for the two clubs to have the same number of members.

Well for this a t-chart type of graph would help but here's how you can do it:

key: ChC = chess club
       CmC = computer club

ChC = 500 members        ChC = losing 30/yr
CmC = 150 members        CmC = gaining 20/yr

year 1 :     ChC     CmC
members: 470   /   170

or you can scrap that, here's the simpler version : 
500 - 30x = 150 +20x

solution: x = 7

Hope this helps!