You call 5 friends, tomorrow they call 5 each. Write an equation.

I'll show  you the percent of change
15 yards to 18 yards
 => 18 - 15 = 3 yards 
=> 3 yards / 15 = .2 * 100% = 20%

100 acres to 140 acres
 => 140 - 100 = 40 acres 
=> 40 /100 = 0.4 * 100% = 40%

$15.60 to $11.70 
=> 15.60 - 11.70 = 3.6 dollars 
=> 3.6 / 15.60 = 0.25 * 100% = 25% 

125 centimeters to 87.5 centimeters
 => 125 cm - 87.5 cm = 37.5 cm  
=> 37.5 / 125 = 0.3 * 100% = 30%

1.6 hours to 0.95 hour 
=> 1.6 - .95 = 0.65 
=> 0.65 / 1.6 = 0.41 * 100% = 41%

and 132 days to 125.4 days  
=> 132 - 125.4 = 6.6 
=> 6.6. / 132 = 0.05 * 100% = 5%