Cups of flour

Jade was baking cupcakes for her class. She has 4 5/4 cups of flour.  For one batch, she used 1 2/3 cups of flour.  On another batch, she used 7/9 of a cup of flour.  How much flour does Jade have left after making the two batches of cupcakes?

Correct answer:

x =  2 ²⁹⁄₃₆ = 101/36

Step-by-step explanation:

$$\begin{gathered} f=4\frac{5}{4}=4+\frac{5}{4}=\frac{4\cdot 4+5}{4}=\frac{16+5}{4}=\frac{21}{4}=5\frac{1}{4}=5.25 \\ a=1\frac{2}{3}=1+\frac{2}{3}=\frac{1\cdot 3+2}{3}=\frac{3+2}{3}=\frac{5}{3}=1\frac{2}{3}\doteq 1.6667 \\ b=\frac{7}{9}\doteq 0.7778 \\ x=f-a-b=\frac{21}{4}-\frac{5}{3}-\frac{7}{9}=\frac{189}{36}-\frac{60}{36}-\frac{28}{36}=\frac{189-60-28}{36}=\frac{101}{36}=2\frac{29}{36}=2.8056 \end{gathered}$$

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