Answer:
The weight of the chocolate is
[tex]=84g[/tex]The percentage of cocoa is
[tex]\begin{gathered} =21\% \\ =\frac{21}{100} \end{gathered}[/tex]To figure out the grams of cocoa it contains, we will use the formula below
[tex]Amount_{cocoa}=Percentage_{cocoa}\times amount_{chocolate}[/tex]By substituting the values, we will have
[tex]\begin{gathered} Amount_{cocoa}=Percentage_{cocoa\times}amount_{chocolate} \\ Amount_{cocoa}=\frac{21}{100}\times84g \\ Amount_{cocoa}=17.64g \\ Amount_{cocoa}\approx17.6g \end{gathered}[/tex]Hence,
The amount of cocoa to the nearest tenth is
[tex]\Rightarrow17.6g[/tex]