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a/ 5/3+ -13/3 =  -8/3 ;  -13/9+27/9 = 14/9 ;  5/6+2-1/3=  10/6

b/ 4/3+7/6 = 15/6 ;  13/5+ 6/3 = 69/15 

c/ 5/6 - -3/-5 = 7/30 ;  -7/4 + -2/9 = -71/36 ;   7/9- 5/6 = -1/18;   -5/20+9/-6 = -7/4

d/ 3+7/4 = 19/4 ;  -3-3/5 = - 18/5

a/3/8*-5/4 = -15/32 ;  -2/7 * -7/5= 2/5 ;  1*3/4*5/6= 5/8

b/ -2*4.5/7= -9/7 ;  4/3* -9/16 = -3/4 ; 2*1/3*4*6/5=16/5

c/ -1/2*2/3*-3/4*6/-5 =-3/10 ;  13/7*-14*5/26 = -5

a/5/6/3/4=10/9;  5/8/-5/4=-1/2 ;   1/3/4= 4/3 ;  7/5/8= 56/5

b/1/38/-1/19= -1/2 ;  13/15/-2.5=-26/75

A= 7/15*3/4-13/20=-3/10 B= -3/5+5/2+17/40=93/40 C= 2/3+5/3*3/2=19/6 

D=(2/3+5/3)*3/2 = 7/2 E= 1+1/2*5-3/4=11/4 F= 1/5+1/2=2/11 G= -3+2/5/4=-13/20

H=1/2-1/3/1/2+1/3=1/5

a/ 10^5*10^7= 10^12  ;  10^11 * 10^-4 =10^7  10^-9*10^3 =10^-6 

10^14*10 =10^15 ;  10^-1*10^-2*10^-3 = 10^-6 ;  10^-3*10^9*10^3 = 10^10