1. 13/14 • 5/18 + 13/14 • 13/18 =
= 13/14 • (5/18 + 13/18) =
= 13/14 • 18/18 = 13/14 • 1 = 13/14
2. 3/8 • 7/11 + 1/11 • 3/8 =
= 3/8 • (7/11 + 1/11) =
= 3/8 • 8/11 = 3/11
3. 100/101 • 99/1100 + 100/101 • 2/1100 =
= 100/101 • (99/1100 + 2/1100) =
= 100/101 • 101/1100 = 100/1100 = 1/11
4. 7/72 • 24/17 - 7/72 • 6/17 =
= 7/72•(24/17 - 6/17) =
= 7/72 • 18/17 = 7/68
5. 3/4 • 5/18 - 2/4 • 5/18 =
= 5/18 • (3/4 - 2/4) =
= 5/18 • 1/4 = 5/72
6. 103/104 • 8/100 - 3/104 • 8/100 =
= 8/100 • (103/104 - 3/104) =
= 8/100 • 100/104 = 8/104 = 1/13