NDA2013MathematicsDeterminantsActual

If 8 x-9 y=20 and 7 x-10 y=9 , then what is 2 x-y equal to?

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Correct answer

A. 10

Step-by-step solution

Substracting two given equations. aligned 8 x-9 y & =20 7 x-10 y & =9 - + & - x+y & =11 or, x=11-y aligned Plug in x=11-y into array r 8 x-9 y=20 8(11-y)-9 y=20 88-8 y-9 y=20 array or, 17 y=68 y=4 and, x=11-4=72 x-y=2(7)-4=10

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