3 1/8: ((4 5/12- 3 13/24) X 4/7 +(3 1/18-2 7/12)X 1 10/12)

3 1/8 : ((4 5/12 - 3 13/24) * 4/7 + (3 1/18 - 2 7/12) * 1 10/17) = 2 1/21) 4 5/12 - 3 13/24 = 4 10/24 - 3 13/24 = 3 34/24 - 3 13/24 = 21/24 = 7/82) 7/8 * 4/7 = 4/8 = 1/23) 3 1/18 - 2 7/12 = 3 2/36 - 2 21/36 = 2 38/36 - 2 21/36 = 17/364) 17/36 * 1 10/17 = 17/36 * 27/17 = 27/36 = 3/45) 1/2 + 3/4 = 2/4 + 3/4 = 5/4 = 1 1/46) 3 1/8 : 1 1/4 = 25/8 : 5/4 = 25/8 * 4/5 = 5/2 = 2 1/2