[m]a+b+c=30[/m]
[m]a+b=17[/m]
⇒
[m]\underbrace{a+b}_{17}+c=30[/m]
[m]17+c=30[/m]
[m]c=30-17=13[/m]
[m]a+b=17[/m]
[m]b=17-a[/m]
По теореме Пифагора
[m]a^2+b^2=c^2[/m]
[m]a^2+(\underbrace{17-a}_{b})^2=13^2[/m]
[m]a^2+(17^2-2\cdot 17\cdot a+a^2=169[/m]
[m]2a^2-34\cdot a+289-169=0[/m]
[m]a^2-17\cdot a+60=0[/m]
[m]a_{1}=12; a_{2}=5[/m]
[m]b_{1}==17-12=5; b_{2}=17-5=12[/m]