Markers are sold in boxes, packs, or as single markets. each box has 10 packs. each pack has 10 markers. draw a picture to show two ways to buy 276 markers

You could buy 276 single markers, you can buy 28 packs of markers, or 3 boxes of marker because 1pack = 10 markers, 10 markers multiplied by 10 packs equals 100. So 1 box would have 100 markers in it and if you took 2 boxes you would be missing 76 markers, so you're better off getting 3 boxes and having 300 markers than being less by 76.

All you do is divide -12/20  by 4/4 which is -3/5