Answer:
.571
Step-by-step explanation:
We need to find the total number of boys
11+5+4 = 20
And the total number of students
11+7+5+4+4+4 = 35
The Probability that the student is a boy is boy/total
P (boy) = boy/total
      = 20/35
      =4/7
      =.571428571
 to 3 decimal places
      =.571