ANSWER:
17 grams of cocoa
STEP-BY-STEP EXPLANATION:
The amount of cocoa will be 21% of the weight of the chocolate bar.
The chocolate bar weighs 84 grams, therefore, the number of grams of cocoa will be 21% of 84, we calculate it below:
[tex]\begin{gathered} 84\cdot21\% \\ \\ 84\cdot\frac{21}{100}=17.01\approx17\text{ g} \end{gathered}[/tex]The chocolate bar contains 17 grams of cocoa
