Chocolates left

What is the equation for Mark? He had 84 boxes of candy to sell, half of which were dark chocolate and the other half white chocolate. He sold 75% of dark chocolate and 40% white. How many did you have left over?

Correct answer:

x =  35.7

Step-by-step explanation:

$$\begin{gathered} n=84 \\ d=n/2=84/2=42 \\ w=n/2=84/2=42 \\ {r}_1=75\%=\frac{75}{100}=\frac{3}{4}=0.75 \\ {r}_2=40\%=\frac{40}{100}=\frac{2}{5}=0.4 \\ x=n-r_1\cdot d-r_2\cdot w=84-0.75\cdot 42-0.4\cdot 42=\frac{357}{10}=35\frac{7}{10}=35.7 \end{gathered}$$

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