Explanation:
first, let's bring everything to the same fraction denominator, which would be 1/8 to cover all.
so, he jogs
3 2/8 miles on Monday
5 5/8 miles on Tuesday
8 0/8 miles on Wednesday
the difference from day to day is
5 5/8 - 3 2/8 = 2 3/8 (subtract the whole numbers and then also the fractional part).
to control :
5 5/8 + 2 3/8 = 7 8/8 = 8
so, he adds every day 2 3/8 miles.
that means in 2 days (from Wednesday to Friday) this will be additional 2×(2 3/8) = 4 6/8 = 4 3/4 miles.
so, he will jog
8 + 4 3/4 = 12 3/4 miles
on Friday.
don't forget, when we write something like 2 3/8. we actuality mean (2 + 3/8). and all rules about handling, transforming and calculating expressions apply.
therefore, e.g
2×(2 3/8) = 2×(2 + 3/8) = 4 + 6/8 = 4 6/8 = 4 3/4