the blue is the answer i just want to know why

Q11. Every month, 20% of rapid transit users switch to driving, while 30% of car drivers switch to rapid transit. What is the long-term proportion of drivers to transit users? P= With s1+s2=1. Thus, we have the system 0.2s1+0.3s2=03s2=2s1s2=(2/3)s1 0.2s10.3s2=03s2=2s1s2=(2/3)s1 s1+s2=1s1+(2/3)s1=1s1=3/5=60% and s2=2/5=40% Thus 60% of the population would use rapid transit and 40% cars