Question 994981
Make a table and use arbitrary number of 10000.
=======G =====NG ===Total
S==== 6375 ===1125===7500
NS====875====1625===2500
Total==7250====2750==10000

Probability random one will graduate is 7250/10000=0.725
Probability that one who graduated studied regularly is 6375/7250=0.879