You can use the weight of the chocolate bar given and find its 77% to get the weight of cocoa used in it.
The weight of cocoa in the given chocolate bar is 70.80 grams.
<h3>How to find the percentage from the total value?</h3>
Suppose the value of which a thing is expressed in percentage is "a'
Suppose the percent that considered thing is of "a" is b%
Then since percent shows per 100 (since cent means 100), thus we will first divide the whole part in 100 parts and then we multiply it with b so that we collect b items per 100 items(that is exactly what b per cent means).
Thus, that thing in number is
× 
Since weight of cocoa = 77% percent of chocolate bar's weight which is 92 gram,
Thus,
×

Thus,
The weight of cocoa in the given chocolate bar is 70.80 grams.
Learn more about percentage here:
brainly.com/question/11549320