[tex]s = v\cdot t[/tex]
[tex]a)\\v = 60\frac{km}{h}\\t = \frac{1}{2} \ h\\\\s = 60\frac{km}{h}\cdot\frac{1}{2} \ h = 30 \ km[/tex]
[tex]b)\\v = 60\frac{km}{h}\\t = 20 \ min = \frac{1}{3} \ h\\\\s = 60\frac{km}{h}\cdot\frac{1}{3} \ h = 20 \ km[/tex]
[tex]c)\\v = 60\frac{km}{h}\\t = 35 \ min = \frac{35}{60} \ h = \frac{7}{12} \ h\\\\s = 60\frac{km}{h}\cdot\frac{7}{12} \ h = 35 \ km[/tex]