Question

How do you do this?

? --> 43 Ca + 0
20 -1 e

Answer 1

\[\huge _{q}^{p}X \rightarrow _{20}^{43}Ca+_{-1}^{0}e\]
You know that mass and energy is conserved in a nuclear reaction, so equate them together
p=43+0
q=20-1
-------------------------
p=43
q=19

\[\huge _{19}^{43}K\]