Answer: 226/88 Ra = 222/86 RN + 4/2 He
Explanation:
To balance the equation, you need to make sure that both sides have the same number of protons and the same atomic masses. Because Radium has 88 protons, the sum of protons on the right side need to add up to 88. Helium has 2 protons, so you need to find the element that has 86 protons (Radon).
The same process is applied to the mass. The atom on the left side of the equation has a mass number of 226, so the mass numbers of Radium and Helium must add up to 226. Because it is stated that Helium has a mass number of 4, the mass number of Radium in this equation is 226. (226-4=222)