Answer:
5 nights
Explanation:
Solve the inequality:
90x + 90(0.1)x + 12x + 30 
 600
 600
Add like terms:
102x + 30 + 90(0.1)x 
 600
 600
Isolate the variables:
102x + 90(0.1)x 
 570
 570
102x + 9x 
 570
 570
111x 
 570
 570
x 
 5.13
 5.13
So, the Lincolns can stay for 5 nights without exceeding $600