What is the 50th term for 10, 13, 16,

First, work out the difference between each term. 13 (Second term of the sequence) -10 (First term of the sequence) is 3, so that means the term is in the 3x table.
Second, work out the deviation from the 3x table.
10 (first term of this sequence) - 3 (first term of the 3x table) = 7
So the sequence is 3n +7
Now replace n with 50, to work out the 50th term
(3*50) + 7 = 50th term
Work out the sum
157 = 50th term

J= r + 9 because since jessica rode 9 more miles than roger, you add 9 miles to rogers mileage.