x1 + x2 = 90
x2+x3 = 140
x1+x3 = 180
x1 + x2 + x2+x3 +x1+x3 = 90+140+180
2(x1+x2+x3) = 2(45+70+90)
x1+x2+x3 = 205
Ответ 205
x1 + x2 = 90
x2+x3 = 140
x1+x3 = 180
x1 + x2 + x2+x3 +x1+x3 = 90+140+180
2(x1+x2+x3) = 2(45+70+90)
x1+x2+x3 = 205
Ответ 205