The given information gives us the clue that deuterium and tritium react together. We need to find the balanced nuclear reaction of deuterium and tritium; however, first, let me explain you what deuterium and tritium are.
Deuterium and tritium are two isotopes of hydrogen having atomic mass of 2 and 3 respectively. Deuterium is represented by
, whereas tritium is written as
.
When deuterium and tritium collide together, they form Helium atom, which is written as
, and also release energy (and shoot out one neutron).
Hence, the balanced nuclear reaction will be the following:

-i