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Start with the first equation

Plug in

and

Plug in

Distribute

Multiply

Combine like terms.

Multiply
EVERY term by the LCD 3 to clear out the fractions.

Combine like terms.
From here you have a simple linear equation. Once you have N, plug this into the second equation to get D. Finally, plug D into the third equation to get Q. Let me know if you need any further help.
Note: you should get D=29, N=81, and Q=87 as an answer.