Nuclear Reactions

Reaction: ${}^{16}_{8}O + {}^{2}_{1}H \rightarrow {}^{A}_{Z}X + {}^{4}_{2}He$
Use conservation of charge (atomic number) and mass number.
Mass number: $16 + 2 = A + 4 \Rightarrow A = 14$
Atomic number: $8 + 1 = Z + 2 \Rightarrow Z = 7$
Z = 7 is nitrogen, so the product nucleus is $_{7}N^{14}$.

X(n, $\alpha$)Li means: X absorbs a neutron and emits an $\alpha$-particle, leaving ${}^{7}_{3}Li$.
${}^{A}_{Z}X + {}^{1}_{0}n \rightarrow {}^{7}_{3}Li + {}^{4}_{2}He$
Mass number: $A + 1 = 7 + 4 \Rightarrow A = 10$
Atomic number: $Z + 0 = 3 + 2 \Rightarrow Z = 5$
Z = 5 is boron, so X is ${}^{10}_{5}B$.