8/13 ÷ 4 4 ÷ 8 / 13 4 / 5 ÷ 3 3 ÷ 4 / 5 15 / 7÷ 5 5 ÷ 15 / 7 21 / 16 ÷ 7 7 ÷ 21 / 16

8 /13 ÷ 4 = 8 / 13 * 1 / 4 = 2 / 13 * 1 / 1 = 2 / 134 ÷ 8 / 13 = 4 / 1 / ( 8 / 13 ) = 4 / 1 * ( 13 / 8 ) = 1 / 1 * ( 13 / 2 ) = 13 / 2 4 / 5 ÷ 3 = 4 / 5 * 1 / 3 = ( 4 * 1 ) / ( 5 * 3 ) = 4 / 15 3 ÷ 4 / 5 = 3 / 1 / ( 4 / 15 ) = 3 / 1 * ( 15 / 4 ) = 3 * 15 / 4 = 45 / 4 15 / 7÷ 5 = 15 / 7 * (1 / 5 ) = 3 / 7 * ( 1 / 1 ) = 3 / 7 5 ÷ 15 / 7 = 5 * ( 7 / 15 ) = 1 * ( 7 / 3 ) = 7 / 3 21 / 16 ÷ 7 = 21 / 16 * ( 1 / 7 ) = 3 / 16 * ( 1 / 1 ) = 3 / 16 7 ÷ 21 / 16 =7 / 1 / ( 21 / 16 ) = 7 * 16 / 21 = 1 * 16 / 3 = 16 / 3