In this task, you need to provide the correct option for a given problem from the provided options.

[EX Q]: Problem: a certain bag contains 100 balls — 50 white , 30 green , 10 yellow , 7 red , and 3 purple . if a ball is to be chosen at random , what is the probability that the ball will be neither red nor purple ? 
Options: a ) 0.9 , b ) 0.75 , c ) 0.6 , d ) 0.8 , e ) 0.5
[EX A]: a

[EX Q]: Problem: the ratio between speed of the two trains is 7 : 8 . if the 2 nd train runs 400 km in 4 hrs , what is the speed of the 1 st train ? 
Options: a ) 87.9 , b ) 87.5 , c ) 87.7 , d ) 87.6 , e ) 43.3
[EX A]: b

[EX Q]: Problem: the ratio of boarders to day students at a school was originally 2 to 5 . however , after a number of new boarders join the initial 120 boarders , the ratio changed to 1 to 2 . if no boarders became day students and vice versa , and no students left the school , how many new boarders joined the school ? 
Options: a ) 30 , b ) 50 , c ) 70 , d ) 80 , e ) 90
[EX A]:
a