Let's define:
y: new value
x: previous value
Given that the value of x is decreased by 40%, then:
[tex]\begin{gathered} \frac{y-x}{x}\cdot100=-40 \\ \frac{y-x}{x}=-\frac{40}{100} \\ y-x=-0.4x \\ y=-0.4x+x \\ y=0.6x \end{gathered}[/tex]Choice B represents the situation
