3 geht so:
\( \frac{4}{3} x-3 =-\frac{1}{3} x+1 \)
<=> \( \frac{5}{3} x-3 =1 \)
<=>  \( \frac{5}{3} x =4 \)
<=>  \(   x =  \frac{12}{5} \)
Also hat S die x-Koordinate  \(   \frac{12}{5} \), Einsetzen
gibt  \(  y = \frac{1}{5} \), also S = ( \(  \frac{12}{5}   ;     \frac{1}{5} ) \).