Simplification: 5m=4(n+2)
So n+2 is a multiple of 5. When n+2=5, n = 3, 16n+ 13 = 6 1. How many students are there in four classes?
When n+2= 10, n = 8,16n+13 = 14 1, it is possible that there are1students in four classes.
When n+2= 15, n = 13,16n+13 = 22 1, it is more likely that there are 221students in four classes.
When n+2=20, n = 18,16n+13 = 30 1, it is less likely that there are 301students in four classes.