F=75 N M=? A=5m/s ​2

Remember    F = ma

75 N-m  = m (5 m/s^2)

75 N-m / 5 m/s^2 =  m           a newton = kg-m/s^2

75 kg-m/sec^2  / 5m/s^2 =   15 kg   =m