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In one hour he would cycle 18Km, therefore in a 1/4 hour the cyclist would ride a 1/4 of 18 = 4.5Km.
This doesn't answer it completely but you have to complete the square. I don't know the answer but there are plenty of videos on how to complete the square online. Hope I could help and sorry if I didn't <span />
The easy way is to count outcomes. Of the 36 equally probable outcomes, 10 are less than or equal to 5, so the probability is 10/36 = 5/18.
