Answer: Choice J
13/20 - 1/2
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Explanation:
Ignore the big X and the shading for now. This figure has 4 rows by 5 columns of rectangles. So there are 4*5 = 20 little rectangles total. Each little rectangle represents 1 brownie.
Then let's say the shaded region represents the amount of brownies Mary receives. We have 13 rectangles shaded in out of the 20 total. This means 13/20 is the fractional amount Mary gets.
She then eats 10 of the 20 total, so she eats 10/20 = 1/2 of the brownies.
Therefore, we end up with the expression 13/20 - 1/2 to represent the fractional amount that Mary still has that she hasn't eaten yet (which is 3/20).
We can say: 13/20 - 1/2 = 13/20 - 10/20 = 3/20
