Answer : Cookie is 50 cents. Step by step explanation : Cookie = x and brownie = y Equation : x + 2y = 2x + y Subtract y on both sides. X + y = 2x Since x + y equals 1, plug that into the equation. 1 = 2x X = 0.5, or 50 cents One cookie costs 50 cents. Please mark brainliest if possible ;)