A uniform meter stick of mass 1 kg is hanging from a
thread attached at the stick's midpoint. One block of
mass m= 3 kg hangs from the left end of the stick, and
another block, of unknown mass M, hangs below the
80 cm mark on the meter stick. If the stick remains at
rest in the horizontal position shown above, what is M ?

Correct  M = 5 kg

Explanation:

According to the data, the first block is 50 cm from the center of the stick and the second block is 30 cm from the center of the stick.

Being in balance (horizontal position) their moments are the same:

M · 30 cm = m · 50 cm ⇒ 30 M = 50 · 3 = 150 ⇒ M = 150/30 = 5 kg

M = 5 kg

God is with you!!!

you cant move and you feel like someones pushing you down onto your bed it can feel like you want to get up but you just can't it can be extremely scary

d.7.5cm is your answer