a+b+c=270
b=3a-20
c=(a+b):2....=>...c=(a+3a-20):2...=>c=(4a-20):2...=>c=2a-10
.........................
a=?b=?c=? a) |___|
b) |___|___|___|-20
c) |___|___|-10
------------------------------
a+3a-20+2a-10=270
6a-30=270
6a=270+30
6a=300
a=300:6
a=50
b=50*3-20
b=150-20
b=130
c=(50+130):2
c=180:2
c=90
50+130+90=
=180+90
=270
