First you have to understand the concepts behind what is going on.
In the first link (the molybdenum one), the atom is undergoing neutron bombardment. This involves bombarding an atom with nuclei in order to produce a transuranic element (which is done in a nuclear reactor)
Basically, large fission chain reaction would have occurred to produce these nuclei. An atom (the molybdenum) is then placed in the reactor and the nuclei bombard the atom. Eventually, the atom will absorb one of the nuclei, which increases the atomic mass by 1 (observe the first equation). However, this addition causes the element to become imbalanced due to an insufficient neutron : proton ratio (in this case, a high ratio due to an excess of protons) and as such will undergo beta decay. The absorbed nuclei will diffuse into a proton and an electron, with proton being absorbed by nucleus and the electron being ejected from the atom. As such, the atomic mass remains the same however the atomic number increases, which produces a transuranic element, which in this case is technetium 99m (observe the second equation)
The second link has equations which are not in the chemistry syllabus (it involves positron emission) but is useful if you do medical physics.