Question 940752
Bully has a pail that contains 40 nails and weighs 175 grams. The same pail with 20 nails weighs 95 grams. How much does Bully's pail weigh with no nails in it? How much does each nail weigh? 
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let x=weight of each nail
let y=weight of pail
..
40x+y=175
20x+y=95
subtract:
20x=80
x=4
..
40x+y=175
40x+2y=190
subtract:
y=15
weight of each nail=4 grams
weight of pail=15 grams