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

The first thing you should know is that by definition complex numbers in their generic form are given by:
 a + bi
 We have then that in this case:
 a = 4
 b = 3
 x = i
 
 The value of x when 4 + 3x is a complex number is:
 i (option 3)