7-[5200:13-5×(360-2×b)]:2=2
[400-5×(360-2×b)]:2=7-2=5
[400-5×(360-2×b)]=5×2=10
400-5×(360-2×b)=10
5×(360-2×b)=400-10=390
(360-2×b)=390:5=78
360-2×b=78
2×b=360-78=282
2×b=282
b=282:2
b=141
Gata!Sper ca ti-am fost de ajutor doar cu atat!!!!