520/21 + 1/3 - 8/63 - 6/7 + 1/9 = (60+21-8-54+7)/63 = 26/63
-41/42-4/7+2/3+1/6-83/84 = (-82 -48+56+14-83)/84= -143/84 =- 1 59/84
-19/24 +7/8 - 41/72 +5/6 -1/3 = (-57 +63 -41 +60-24)/72=-1/72
11/18 +5/9 -1/2 -13/15 -47/90= (55+50-45-78-47)/90 = -65/90= -13/18
-43/88 -1/2 +3/4 +21/44 +8/11 = (-43 -44 +66+42+64)/88=85/88
+1/2 -25/33 +2/3 -7/22 +59/66 =(33 -50 +44-21+59)/66= 65/66
-23/48 +5/8 -89/96 -11/16 +5/6 = (-46+60-89-66+80)/96 = -61/96
-3/4 -1/6 -97/120 +7/12 -23/30 = (-90- 20 -97 +70 -92)/120 =
=-229/120= - 1 109/120