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 ratio between the speeds of two trains is 7 : 8. If the second train runs 400 kms in 4 hours, then the speed of the first train is:

 Option A: 70 km/hr

 Option B: 75 km/hr

 Option C: 84 km/hr

 Option D: 87.5 km/hr

 Option E: 88.5 km/hr
Option D

Question: The average age of 15 students of a class is 15 years. Out of these, the average age of 4 students is 14 years and that of the other 10 students is 16 years, The age of the 15th student is

 Option A: 11

 Option B: 12

 Option C: 9

 Option D: 14

 Option E: 15
Option C

Question: A line has a slope of 3/4 and intersects the point W (-12, -39). At which point does this line intersect the x-axis?

 Option A: (40,0

 Option B: (30,0

 Option C: (0,40

 Option D: (40,30

 Option E: (0,30

Option A