The ratio of \(a\) to \(b\) is \(4\) to \(5,\) where \(a\) and \(b\) are positive. If \(x\) equals \(a\) increased by \(25\) percent of \(a,\) and \(m\) equals \(b\) decreased by \(20\) percent of \(b,\) what is the value of \(\dfrac{m}{x}?\)

A. \(\dfrac25\)
B. \(\dfrac34\)
C. \(\dfrac45\)
D. \(\dfrac54\)
E. \(\dfrac32\)

Answer: C

Source: Veritas Prep