firstly. make your unknown number X.
95% can be represented as 95/100 or 0.95
so 95% of X is 76...
0.95 × X = 0.76
X = 0.76 ÷ 0.95
X = 0.8
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for the second question.
(17 ÷ 20.4) and times it by 100 to get a percentage.
