To calculate the total area that needs to be painted, we first find the surface area of the walls and then add the surface area of the garage door and the small door.
Surface area of the four walls:
Wall 1: 30 ft x 9 ft = 270 square feet
Wall 2: 30 ft x 9 ft = 270 square feet
Wall 3: 35 ft x 9 ft = 315 square feet
Wall 4: 35 ft x 9 ft = 315 square feet
Total surface area of the walls = 270 + 270 + 315 + 315 = 1,170 square feet
Surface area of the large garage door:
13 ft x 8 ft = 104 square feet
Surface area of the small door:
7 ft x 4 ft = 28 square feet
Now, let's find the total surface area that needs to be painted:
Total surface area = 1,170 + 104 + 28 = 1,302 square feet
Since Lavonne needs to apply three coats of paint, we need to multiply the total surface area by 3:
Total area to be painted with three coats = 1,302 square feet x 3 = 3,906 square feet
Now, we can calculate how many cans of paint Lavonne needs to buy, given that each can covers 425 square feet:
Number of cans needed = Total area to be painted / Coverage per can
Number of cans needed = 3,906 square feet / 425 square feet per can
Number of cans needed ≈ 9.19
Since you cannot buy a fraction of a can, Lavonne needs to round up to the nearest whole number of cans.
Lavonne needs to buy approximately 10 cans of paint to paint the inside of her garage with three coats and achieve full coverage.