Option 1 -> Uses variables X and Y without proper notation for quantities.
Option 2 -> Uses variables X and Y without proper notation for quantities.
Option 3 -> Uses proper notation Qx and Qy for quantities, with coefficients 5 and 10 representing prices.
Option 4 -> Uses proper notation but with different price coefficients (10 and 5 reversed).
Hence, 5Qx + 10Qy = 100 -> This is the correct budget line equation where Px = 5 (price of good X), Py = 10 (price of good Y), and M = 100 (income/budget). The budget line equation format is: Px·Qx + Py·Qy = M, where Qx and Qy represent quantities of goods X and Y respectively. This equation shows all combinations of goods X and Y that a consumer can purchase with the given budget and prices. -> correct