Answer:
24 students are right-handed.
Step-by-step explanation:
30 total
 1 left + 4 right = 5
+1 left + 4 right = 5
 2 left + 8 right = 10
+1 left + 4 right = 5
 3 left + 12 right = 15
+1 left + 4 right = 5
 4 left + 16 right = 20
+1 left + 4 right = 5
 5 left +20 right = 25
+ 1 left + 4 right = 5
6 left +24 right = 30