Similar shapes can be different sizes, but look the same. Congruent shapes are the exact same as eachother.
This equation is separable, as

Integrate both sides; on the left, expand the fraction as

Then


Since
, we get

so that the particular solution is

Answer:
ok so it's telling you that for 10 folder it cost 1.50 cents each and for 20 it's 3.50 and 30 5$ and 40 6$ and it's basically telling you that what ever your reading you have to think how much did that person spend or bought and how much do u think each folder it's so u have to figure out how many does each cost of cents for each folder.
There are 52 weeks in a year, so 52x represents how much she earns in a year.