[tex]\begin{gathered} 60+61+m<4=180 \\ 121+m<4=180 \\ m<4=180-121 \\ m<4=59 \\ \\ \text{ and then } \\ m<4+60=m<3,\text{ by internal external angles} \\ 59+60=m<3 \\ 119=m<3 \\ \\ \text{then} \\ m<3+m<2=180 \\ m<2=180-119 \\ m<2=61 \\ \\ \text{and } \\ m<1+m<2+60=180 \\ m<1+61+60=180 \\ m<1+121=180 \\ m<1=180-121 \\ m<1=59 \\ \\ \\ \text{ thus } \\ \\ m<1=59 \\ m<2=61 \\ m<3=119 \end{gathered}[/tex]
