Answer:
1/3
Step-by-step explanation:
[tex]\left[\begin{array}{cccc}Bought\ Lunch&Boys&Girls&Total\\0\ up\ to\ 10&10&5&15\\10\ up\ to\ 20&20&25&45\\Total&30&30&60\end{array}\right][/tex]
The number of boys who bought 10 to 20 lunches is 20.
The total number of students is 60.
So the probability is 20/60 = 1/3.