Answer:
[tex]0.495ms^{-2[/tex]
Explanation:
According to the newton's second law of motion we can apply F=ma hear
Force = mass * acceleration
(assume the piano is moving left side )
←F = ma
[tex]F(pull) + F (push) = M * a\\77.5 + 48.7 = 255*a\\a = 0.495ms^{-2}[/tex]