When is the sum of two negative mixed numbers an integer

The price of a dozen eggs was $1.63. suppose the price increases m dollars per dozen and then the price decreases $0.12 per dozen. which expression represents the current price of eggs after the two price changes?

8litres of paint can cover 129.6 m². how much paint is required to paint an area of 243m²?

What is y-5=3(x+1) in slope intercept form