It's been estimated that if you consume an extra 3,500 calories, you will gain 1 pound of fat. one can of soda contains 40 grams of sugar. sugar has 4 calories per gram. if a person drinks a six-pack of soda every day, how many pounds will he or she gain in 1 year?

We know that
1 can of soda> 40 grams of sugar
if 1 gram sugar>has 4 calories
40 grams (1 can of soda)> X
X=40*4=160 calories
then 
1 can of soda> has 160 calories
six-pack of soda every day> 6*160=960 calories every day

in one year> 960*365=350400 calories in one year

if 3500 calories> 1 pound of fat
350400 caloriesX
X=350400/3500=100.11 pound
In one year she or he will gains 100.11 pound of fat

the answer is 100.11 pound