It would be better to convert each measurement into its smallest measure. In this case let us convert yards and feet into inches.
1 yard = 36 inches
1 foot = 12 inches
6 yards = 216 inches
9 feet = 108 inches
216 inches + 108 inches + 4 inches = 328 inches
328 inches * 2 = 656 inches
656 inches / 36 = 18.22
18 * 36 = 648 inches is equivalent to 18 yards.
656 - 648 = 8 inches.
6yd 9ft 4in times 2 equals 18 yards and 8 inches.
