To find \( M - N \), we first need to write out the expressions for \( M \) and \( N \):
\[ M = 10xy + 3y - 4 \] \[ N = 9y + 5xy + 14 \]
Now, we subtract \( N \) from \( M \):
\[ M - N = (10xy + 3y - 4) - (9y + 5xy + 14) \]
Distributing the negative sign in front of \( N \):
\[ M - N = 10xy + 3y - 4 - 9y - 5xy - 14 \]
Now, combine like terms:
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For \( xy \) terms: \[ 10xy - 5xy = 5xy \]
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For \( y \) terms: \[ 3y - 9y = -6y \]
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For constants: \[ -4 - 14 = -18 \]
Putting it all together, we have:
\[ M - N = 5xy - 6y - 18 \]
Therefore, the result is:
\[ \boxed{5xy - 6y - 18} \]