7/9+5/16=
3/8+2/9=
1/9+1/27=
3/30+3/20=
7/21+4/15=
13/20+5/8=
5/18+7/15=
4/5+21/100=
13/18+5/12=
3/11+35/66=
11/20+17/18=

1) 7/9+5/16 = (7*16 + 5*9) / (9*16) = 157/144 = 1 13/144

2) 3/8+2/9= (3*9 + 2*8) / (8*9) = 43/72

3) 1/9+1/27= 3/27 + 1/27 = 4/27

4) 3/30+3/20= (3*2 + 3*3)/60 = 15/60 = 1/4

5) 7/21+4/15= (7*5 + 4*7) / (3*5*7) = 63/105

6) 13/20+5/8= (13*2 + 5*5) / (2*4*5) = 51/40 = 1 11/40

7) 5/18+7/15= (5*5 + 7*6) / (3*5*6) = 67/90

8) 4/5+21/100= 80/100 + 21/100 = 101/100 = 1 1/100

9) 13/18+5/12= (13*2 + 5*3) / (6*2*3) = 41/36 = 1 5/36

10) 3/11+35/66= 18/66 + 35/66 = 53/66

11) 11/20+17/18= (11*9 + 17*10) / (2 * 9 * 10) = 269 / 180 = 1 89/180