1. ВС/12 = 6/15
ВС = 12*6/15 = 24/5 =4,8
4/MN = 6/15
MN = 4*15/6 = 10
2.
АВ = х+х+6 = 2х+6
х+6/( 2х+6) = 10/15 = 2/3
(2х+6)*2 = 3(х+6)
4х+12 = 3х+18
4х-3х = 18-12
х = 6
АВ = 2*6+6 = 18
ВС = 8+у, где у = ЕС
8/8+у= 10/15 = 2/3
2(8+у) = 8*3
8+у = 12
у = 4
ВС = 12
3.