How do you turn 5/8 too a percentage?

You divide the numerator (top number) by the denominator (bottom number) and you should get a decimal now all you have to do is move the decimal point two places the right and you should get your answer

Amna is the fastest typist

Explanation:

Amna:
15 mins = 710 words
1 min = 710/15
1 min = 47 word

Sara:
18 mins = 810 words
1 min = 810/18
1 min = 45 words

Uzma:
20min = 780words
1 min = 780/20
1 min = 39 words

Therefore, we can see that Amna is the fastest typist out of the three.