The first two hours cost 250$, and then every additional hour costs 50$.
So, Eli will surely spend 250$ for the first two hours, and since she has a budget of 600$, she can spend
[tex] 600-250 = 350 [/tex]
extra dollars. Since every extra hour costs 50$, she can book
[tex] 350 \div 50 = 7 [/tex]
extra hours.