ANSWER
820 + 110.50x = E
1205 + 75.50x = K
Step-by-step explanation
Let x represent the number of nights spent in a hotel.
Let E represent the total amount Elisa spends.
Let K represent the total amount Katy spends.
We have that Elisa paid $820 for her plane ticket and $110.50 per night for her hotel.
This means that the total amount that Elisa spent after x nights is:
820 + 110.50 * x = E
=> 820 + 110.50x = E
We also have that Katy paid $1205 for her plane ticket and $75.50 per night for her hotel.
This means that the total amount that Katy spent after x nights is:
1205 + 75.50 * x = K
1205 + 75.50x = K
The system of equations that model the amount of money that Elisa and Katy spend during their trips is:
820 + 110.50x = E
1205 + 75.50x = K