Question

A girl walks 12 km at speed of 3km per hour. What change should she make in her speed to take an 1 hour less

Answer 1

Please see the attachment

Answer 2

Formula of speed is
$\frac{distance}{time} = speed$
$\frac{12}{x} = 3$
x=4
if she take 1hour less then
$\frac{distance}{time} = speed$
$\frac{12}{3} = speed$
speed=4km/hour
so speed will increase by 1km/hr