You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

Question: The average runs scored by a batsman in 20 matches is 40. In the next 10 matches the batsman scored an average of 20 runs. Find his average in all the 30 matches?

 Option A: 31

 Option B: 46

 Option C: 88

 Option D: 33.33

 Option E: 12
Option D

Question: In the arithmetic sequence t1, t2, t3, ..., tn, t1=23 and tn= tn-1 - 3 for each n > 1. What is the value of n when tn = 8?

 Option A: -1

 Option B: 6

 Option C: 10

 Option D: 14

 Option E: 20
Option B

Question: P is able to do a piece of work in 10 days and Q can do the same work in 12 days. If they can work together for 5 days, what is the fraction of work left?

 Option A: 7/12

 Option B: 5/12

 Option C: 1/12

 Option D: 3/12

 Option E: 1/2

Option C