Final answer:
Myrtle Wilson's reason for having an affair is not directly stated in 'The Great Gatsby', but she seems to seek escape from her current life and to attain wealth and higher social status through her relationship with Tom Buchanan.
Step-by-step explanation:
Myrtle Wilson in F. Scott Fitzgerald's The Great Gatsby does not explicitly state her reasons for having an affair in the novel. However, it can be deduced through her actions and dialogue that Myrtle is dissatisfied with her life and sees her affair with Tom Buchanan as an escape from her dreary existence.
She strives for a life of wealth and status, which she believes Tom represents, in contrast to her husband George's impoverished lifestyle.
These reasons reflect the dissatisfaction and desire for freedom that some individuals felt during the Roaring Twenties.