23 x 10% 8 written as a scientific notation

It takes jonas 7 1/4 minutes to run the mile. it takes mario 8 5/12 to run the mile. how much faster is jonas than mario? 5/6 minute 1 1/3 minutes 1 1/6 minutes 1 1/2 minutesi will give points and brainlest

Ineed i been stuck on this question since yesterday

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).