[tex]distance\ = \ 9 \ km\\ speed = 40 \ \frac{ km}{h}\\time =? \\\\speed = \frac{distance }{time} \\\\speed \cdot time= distance \\ \\ time =\frac{distance }{speed} \\\\time = \frac{9 \ km }{40 \ \frac{km}{h}}= \frac{9}{40}\ h =\frac{9}{40}*60 \ min =\frac{9}{2}*3 \ min =\frac{27}{2}\ min =13.5 \ min [/tex]
