algebrajunkie

Brandon has 3 inventions, one saves 30 percent on fuel; a second saves 45% a third saves 25%. If he uses all three inventions at once, what percent can he save on fuel? do I add all of the percentages together and divide by 3? =1/3 or 3%? or is it 100%?

Shellie pays $4.00 for a square piece of wood, which she makes into a stop sign by cutting the corners off. what is the cost of the wasted part? I don't even know where to begin? do I take $4.00*1/8....which equals half and subtract that from 4.00...getti...

thank you so much!