You are working on decorating your home for the holidays. You enjoy hanging lights, and so far have invested in $75 worth of lights. You notice a sale that you can get strands of lights for $5 a box this week. Write an expression that describes your total investment(money spent) in lights, depending on how many boxes (b) of lights you buy.
Total Investment Expression: ______
What is your total investment if you purchase 6 additional sets of lights? $_____