If you put an object that weighs 8 grams on one side of a balance scale, you would have to put about 20 paper clips on the other side to balance the weight. How many paper clips would balance the weight of a 10-gram object?
You're basically saying that 8 grams is equivalent to 20 paper clips.
Therefore 10 grams would be equivalent to (10/8) x 20 = 25 paper clips.
Or alternatively you could say 20 paper clips weigh 8 grams, so each paper clip weighs (8/20) = 0.4 grams. Therefore if you increase the weight of the object from 8 gram to 10 gram, thats an increase of 2 grams which means adding (2/0.4) = 5 more clips.