6) AB:BC:AC = 6:4:3
A₁B₁:B₁C₁:A₁C₁ = 6t:4t:3t
6t+4t+3t = P(A₁B₁C₁) = 91
13t = 91
t = 91/13 = 7
A₁B₁ = 6t = 42
B₁C₁ = 4t = 28
A₁C₁ = 3t = 21
7) M₁K₁:K₁N₁:M₁N₁ = 9t:7t:8t
M₁K₁+K₁N₁ = 48
9t+7t = 48
16t = 48
t = 3
M₁K₁ = 9t = 27
K₁N₁ = 7t = 21
M₁N₁ = 8t = 24
8)
M₁K₁:K₁N₁:M₁N₁ = 9t:7t:8t
M₁K₁-K₁N₁ = 6
9t-7t = 6
2t = 6
t = 3
M₁K₁ = 9t = 27
K₁N₁ = 7t = 21
M₁N₁ = 8t = 24