The answer I think is D but use the app photo math very useful:)
Answer:
If your trying to simplify then your answer would be 
Answer: Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other
Hope it helps:) I got it right on my test btw
Step-by-step explanation:
Answer:
x = 5
y = 4
Step-by-step explanation:
multiply the second equation by -1 and add the first equation to eliminate "x"

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Replace "y" in the first equation:




Hope this helps