「」。
What would you do if I said no?
Literal
I [subject-が] 'no' [quotative-と] say-[if-たら] how do.
嫌だ ('don't want [to], refuse') is the standard N4 'no' that expresses personal refusal. たら is the hypothetical/temporal conditional. どうする literally 'how [do you] do' is a rhetorical question meaning 'what would you do?' A challenge or hypothetical probe.