The ratio of a to b is 4 to 5, where a and b are positive. If x equals a increased by 75 percent of a, and m equals b decreased by 80 percent of b, what is the value of m/x?  Choose the correct answer:
A) 1 / 7
B) 3 / 4
C) 4 / 5
D) 5 / 4
E) 3 / 2

Rationale: "a / b = 4 / 5 m / x = ( 1 / 5 ) * 5 / ( 7 / 4 ) * 4 = 1 / 7 the answer is a ."
Answer: A