Mohon bantuannya ya buat no. 1

semoga bisa membantu ya..

ΣF = ma
a = F / (mA + mB)

Tinjau benda B!
F kontak = mB a
= mB F / (mA + mB)
= (3 kg)(50 N) / (7 kg + 3 kg) = 15 N