We can convert the fraction to a denominator of 100, since percents are parts of 100.
39 * 2 = 78
50 * 2 = 100
So we have 78/100 or 78%
The range refers to the value of y for which x is define.
So let y=f(x),

Try making x the subject to obtain,

x is defined for all real values of y greater than
0.
Hence the correct answer is D.
The range would be the difference between the lowest age and the highest age.
The highest age is 76, the lowest age is 30
The range is 76 - 30 = 46