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Answer

$$-\frac{7}{72}-\frac{9}{9}x=\frac{-72x-7}{72}$$

Explanation

Tap the blue circles to see an explanation.

$$ \begin{aligned}-\frac{7}{72}-\frac{9}{9}x& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-\frac{7}{72} - \frac{ 9 : \color{orangered}{ 9 } }{ 9 : \color{orangered}{ 9 }} \cdot x \xlongequal{ } \\[1 em] & \xlongequal{ }-\frac{7}{72}-\frac{1}{1}x \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-\frac{7}{72}-x \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{-72x-7}{72}\end{aligned} $$
①
Divide both the top and bottom numbers by $ \color{orangered}{ 9 } $.
②
Remove 1 from denominator.
③

Subtract $x$ from $ \dfrac{-7}{72} $ to get $ \dfrac{ \color{purple}{ -72x-7 } }{ 72 }$.

Step 1: Write $ x $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: To subtract raitonal expressions, both fractions must have the same denominator.
We can create a common denominator by multiplying the second fraction by $\color{blue}{72}$.

$$ \begin{aligned} \frac{-7}{72} -x & \xlongequal{\text{Step 1}} \frac{-7}{72} - \frac{x}{\color{red}{1}} = \frac{ -7 }{ 72 } - \frac{ x \cdot \color{blue}{ 72 }}{ 1 \cdot \color{blue}{ 72 }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ -7 } }{ 72 } - \frac{ \color{purple}{ 72x } }{ 72 }=\frac{ \color{purple}{ -72x-7 } }{ 72 } \end{aligned} $$
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