The third choice is very useful. It's valid because two things that are both equal to 'y' are equal to each other, and it can be easily solved to find 'x'.
Answer:
see explanation
Step-by-step explanation:
Using the cosine and tangent ratios in the right triangle
cos41° =
=
= 
Multiply both sides by VX
VX × cos41° = 7 ( divide both sides by cos41° )
VX =
≈ 9.3
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tan41° =
=
= 
Multiply both sides by 7
7 × tan41° = WX, thus
WX ≈ 6.1
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The sum of the 3 angles in a triangle = 180°
Subtract the sum of the given angles from 180° for ∠ X
∠ X = 180° - (90 + 41)° = 180° - 131° = 49°
(10 + y)² - y² = 3x + 12
(10 + y)·(10 + y) - y² = 3x + 12
10² + 20y + y² - y² = 3x +12
100 + 20y = 3x + 12
100 - 12 = 3x - 20y
3x - 20y = 88
3x - 20 y - 88 = 0 (I suppose it is that one, simplifyied and in order of the letters, or that it you at the previous step)