To find a percentage change:
[tex] \frac{original \: value - new \: value}{original \: value}  \times 100\%[/tex]
In this case:
[tex] \frac{140 - 110}{140}  \times 100\% \\   =  \frac{30}{140}  \times 100\% \\  =  \frac{3}{14}  \times 100\% \\  = 21.429...\%[/tex]
The percentage decrease would be 21.429%.
Hope it helps!