SOLUTION: (2/5+3/8)-3/20 I'm having a hard time trying to solve this problem I keep getting the wrong answer

Question 832577: (2/5+3/8)-3/20
I'm having a hard time trying to solve this problem I keep getting the wrong answer
Found 2 solutions by Alan3354, KMST:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
How did you get your answer?
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!

To add or subtract fractions, you need to express them as equivalent fractions with the same denominator.
, and
I chose as a common denominator to add and because it is a multiple of both denominators :
.
The fact that is also a multiple of , the denominator of was just a lucky coincidence.
Finally, when we get as a result we realize that and are both multiples of , and that
.
Since , we express the fraction in the simpler way of writing it.
If and had any factor in common, I would simplify the fraction further, but and have no common factor.

NOTE ON EQUIVALENT FRACTIONS:
of a pizza cut into 5 equal slices is 2 slices.
Each slice is of the pizza.
You could mark your portion of that pizza by sprinkling oregano on those 2 slices.
If each one of all 5 slices is split into 8 equal wedges, the pizza will be split into
very thin pizza wedges, all the same size.
Each one of those 40 thin slivers of pizza is of the pizza.
Your portion, which was of the pizza, is now made up of
of those thin slivers, so it is .
It may be harder to eat that way, but .
The denominator (the bottom number) got multiplied times 8, because each of the original slices was split into 8 equal slivers of pizza, and now there is a total of such slivers to the whole pizza.
At the same time, the numerator (the top number, and the number of pieces in your portion was also multiplied times 8.
Multiplying numerator and denominator times the same number, you get an equivalent fraction. It has the same value. It is the same number, just written in a different way.
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