There are 1 questions in this calculation: for each question, the 1 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ (90 - \frac{(X + y)}{2} - 6)z\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = 84z - \frac{1}{2}Xz - \frac{1}{2}yz\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( 84z - \frac{1}{2}Xz - \frac{1}{2}yz\right)}{dx}\\=&0 + 0 + 0\\=&0\\ \end{split}\end{equation} \]

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