Solution:The top number (242) is the mass number (A), which represents the total number of protons and neutrons in the nucleus.
The bottom number (94) is the atomic number (Z), which represents the number of protons in the nucleus. The atomic number also defines the element.
To find the number of neutrons (N), we can use the following formula: N=A−Z
Substituting the values for ₉₄Pu²⁴²: N=242−94