The total number of alpha and beta-particles given out during given nuclear transformation is-
(238)U ---> (214)PB
(238)U ---> (214)Pb
U -238 to Pb 214 results in decrease in atomic mass by 24 which means 6 alpha decays as each alpha decay will decrease mass by 4 unit
But every alpha decay will also decrease atomic number by 2 units so 6 alpha decays will decrease it by 12 units
However atomic number change from Uranium to Lead is of 10units
Now each beta decay increase the atomic mass by 1 unit as one electron decay from nucleus will result in increase in one proton in the nucleus.
It means to make 12 unit decrease in atomic number ,two beta decays are needed. [attachment id=0 msg=2571]