So if Angela entered the same restaurant 4 times, we have 4 "instances" of her entering the restaurant.
Each instance, she ordered a salad. The price of this salad is unknown, so we'll say the price is "S".
Each instance, she payed a $5 tip.
So we have 4 instances of spending S, and 4 instances of spending 5.
We know this totals 54.
Knowing all of this information, we can write our equation like this:
4(S + 5) = 54
Divide
S + 5 = 13.50
Subtract
S = 8.50
The cost of salad is $8.50
