Yes. since half of 50 is 25 it is correct to say that 18 is less than half
Assume x are Erica's classes & y are Bo's classes.
x+y=35
x=2y-13
Replacing the value of x into the first equation
2y-13+y=35
3y=35+13
y=16 classes
x=2*16-13=19 classes
2 maybe i have no idea sorry
I need to see more in order for me to answer this question for you...