12.
[tex]v = 400\frac{km}{h} = \frac{400 \ km}{60 \ min} =\frac{20}{3} \ \frac{km}{min} =6,(6) \ \frac{km}{min}\\t = 18 \ min\\\\s = v\cdot t\\\\s = \frac{20}{3} \ \frac{km}{min}\cdot18 \ min}\\\\\boxed{s = 120 \ km}[/tex]
13.
[tex]v = 260\frac{km}{h}\\t = 0,5 \ h\\\\s = v\cdot t\\\\s = 260\frac{km}{h}\cdot0,5 \ h\\\\\boxed{s = 130 \ km}[/tex]
