Probability

if getting a student good in maths is called a success,

 then

p(success)=1/2

so

prob (failure)=1-(1/2)=1/2

if out of 18, exactly 10 students are good in maths , so we have,

10 successes and 8 failures

so

the reqd prob distribution will be

p(X=10)=

for at least 10,

 you can consider,

10 successes, 11 successes..... 18 successes and write the answer in the same manner as above.

similarly for the other parts.