TASK DEFINITION: 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.
PROBLEM: Question: A tank holds x gallons of a saltwater solution that is 20% salt by volume. One Fourth of the water is evaporated, leaving all of the salt. When 5 Gallons of water and 10 gallons of salt are added, the resulting mixture is 33 1/3 % salt by volume. What is the value of x?

 Option A: 37.5

 Option B: 75

 Option C: 100

 Option D: 150

 Option E: 175

SOLUTION: Option B

PROBLEM: Question: If the operation ∆ is defined by a ∆ b = (b - a)^2/a^2 for all numbers a and b, and a ≠ 0, then what is the result when we evaluate this expression: (-5) ∆ (5 ∆ −5) ?

 Option A: 49/9

 Option B: 49/16

 Option C: 81/16

 Option D: 81/25

 Option E: 100/81

SOLUTION: Option D

PROBLEM: Question: In how many no. between 100 and 1000 exactly one of the digits is 3?

 Option A:  648

 Option B:  512

 Option C:  252

 Option D:  225

 Option E:  26

SOLUTION:
Option D