mohon bantuannya yah !!!!

a = F / (m₁ + m₂ + m₃)
   = 30 N / (10 kg + 5 kg + 15 kg) = 1 m/s²

F - Fk₁₂ = m₁a
Fk₁₂ = F - m₁a
        = 30 N - (10 kg)(1 m/s²) = 20 N

Fk₂₁ - Fk₂₃ = m₂a
Fk₂₃ = Fk₂₁ - m₂a
        = (20 N) - (5 kg)(1 m/s²) = 15 N
atau
Fk₃₂ = m₃a
        = (15 kg)(1 m/s²) = 15 N

Fk₁₂ / Fk₃₂ = (20 N) / (15 N)
Fk₁₂ : Fk₃₂ = 4 : 3