Add 7 to both sides
12+7 = 19
Y = 19
Answer:
See Explanation
Step-by-step explanation:

Answer: b. helium nucleus
Helium nucleus is the particle that is being emitted in an alpha radiation. This helium nucleus then transforms and becomes decays that are also known as alpha decays. The alpha particle maybe similar to helium nucleus however, it does not have electrons surrounding it.
Answer:
29°
Step-by-step explanation:
SMH sorry it wasnt 