Based on the given situation, if x is number of kilograms of lobster, you can write the following expressions:
51 + 5x cost in the first restaurant
33 + 8x cost in the second restaurant
In order to determine the value of x which makes the cost the same in both restaurants, equal the previous expressions and solve for x:
51 + 5x = 33 + 8x subtract 33 both sides and 5x subtract both sides
51 - 33 = 8x - 5x simplify
18 = 3x divide by 3 both sides
18/3 = x
6 = x
x = 6
Hence, the weight of the lobster is 6 kg.
The cost of the dinner is:
51 + 5(6) = 51 + 30 = 81
Hence, the cost of the dinner is $81
