Hey!
I'm posting this answer so it helps you with future questions...
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To find the best answer we want to look at given rhombus' angles...
[Given]: A rhombus contains 2 angles > than 90*, and 2 angles < than 90*
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We see that A (6), would be incorrect, because none of the angles are above 90*, and this answer shows that 7(6) + 33 = 75
And
11(6) + 21 = 87
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We also see that B (5) would be incorrect because yet again, because none of the given angles are above 90* as we see in the photo (and that we proved with A's equation)
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We see that C (7) would be the correct answer because it keeps one angle above 90* and one angle below 90*
7(7) + 33 = 82
11(7) + 21 = 98
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And finally we see that D (8) would be incorrect because with 8, 2 angles (for a rhombus) are normally under 85* and the other 2 angles are normally above 95*
7(8) + 33 = 89
11(8) + 21 = 109
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Hope this helps you understand this better...
Have a great day, and keep calculating away...