Question 1143802
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From this fragment of the condition  ". . . 10 walk to school and 9 of the walkers are right-handed" 

one may conclude that one (and only one) of 10 walking to school is left-handed.


Therefore, the answer to  i)  is  P = {{{1/10}}} = 0.1 = 10%,   and 

           the answer to  ii) is  P = {{{1/10}}} = 0.1 = 10%.



Next, since of 30 students 26 are right-handed (given), it means that 4 = 30-26 are left-handed.


Of these 4 left-handed, only one walks to school, as we established ABOVE.

Hence, the rest  4-1 = 3 left-handed do not walk to school, giving answer to iii) :

    P (does not walk to school if we know the student is left-handed) = {{{3/30}}} = {{{1/10}}} = 0.1 = 10%.
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All questions are answered -- the problem is solved.