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12

12

I see a lot of rectangles, but no squares.

10+5 = 15
15-7 = 6
6 x 3 -13 = 5

Add up all 3 totals = 26

Take 26, divide that by 2 and subtract 9 = 4

4 x 2 - 1 = 7

7 minus the number of days in a week and you’ll reach your answer to the above question:

Zero “0”