Question

Thaddeus shakes his head as he pays $12.37 to the clerk for lunch. Complaining to a friend, Thaddeus says, “Do you realize that is 0.2% of my monthly income?” His friend replies, “I think you made a mistake. That should be 2%. You messed up on the decimal point.” (a) Assuming Thaddeus is not wrong, what is his monthly income? (b) If Thaddeus’ friend is correct, what is Thaddeus’ monthly income?

Answer 1

a) If Thaddeus is not wrong, his monthly income is $6,185.

x/12.37 = 100/0.2

0.2x = 1237

x = 1237/0.2x

x = 6,185

b) If Thaddeus's friend is correct, Thaddeus's monthly income is $618.5

x/12.37 = 100/2

2x = 1237

x = 1237/2x

x = 618.5

Answer 2

Pretty simple question, just set up the equation.
A) say Thad is right then equation is as follows:
X * 0.002 = 12.37
Where X is monthly income.
So to solve for X just divide 12.37 by 0.002 (0.2%)
6185$ per month. Which no offense to Thad, but means he’s probably some kind of software engineer or investment banker if he’s making that much a month. (Unlikely for Thad)

B) if he’s wrong then just set up again
X * 0.02 = 12.37
Where x = monthly income
So x= $618.5
More likely given he’s complaining about a 12$ lunch when inflation has the yelp one ($) sign restaurants charging 15 or 16 just for a meal with tip and tax.
Anyways my rant aside hope this helps.