Let the mass of electron is halved, mass of proton is doubled and mass of neutron is made three fourth of original mass. Mass number of O-16

Mass of electron is negligible.It is not considered while calculating mass number ;Actual mass number = 8 p + 8 n = 16 ; New mass number : 8×2 p+34×8n=22  6 units increase for 16  % increase =100×616=37.5%