What is the missing number in the nuclear reaction shown below 175 78 pt?

Above question is incomplete. Complete question is
What is the missing number in the nuclear reaction 175 78 pt -- 4 2 He plus 76 Os?

Solution:

Reaction involved in present nuclear event is 
175 78 Pt      →          4 2 He          +          76 Os

In above nuclear reaction, atomic mass number of Os is missing. The atomic mass number of Os = 175 - 4 = 171

Thus, complete nuclear can be written as
175 78 Pt      →          4 2 He          +       171  76 Os

It’s b. mass i searched it up

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na