А)) (2 7/12+ 3/5) - (1 8/15 - 1/4)=
2 (7•5)/(12•5)+ (3•12)/(5•12) -
1 (8•4)/(15•4) + (1•15)/(4•15)=
2 35/60+ 36/60- 1 32/60 + 15/60=
2 71/60- 1 32/60+ 15/60=
2 39/60+ 15/60=
2 54/60= 2 9/10= 2,9
Б)) (25/27- 1/2) - (5/9- 1/6)=
25/27- (1•3)/(2•3) - (5•3)/(9•3)+ 1/6=
25/27- 3/6- 15/27+ 1/6=
10/27- 2/6= 10/27- 1/3=
10/27- (1•9)/(3•9)=
10/27- 9/27= 1/27
В)) (25/36- 1/8) -(5/24+ 2/9) =
25/36- (1•3)/(8•3) - 5/24- (2•4)/(9•4)=
25/36- 3/24- 5/24- 8/36=
17/36- 8/24= 17/36- 1/3=
17/36- (1•12)/(3•12)=
17/36- 12/36= 5/36
Г)) (3 7/8 - 3/20) + (5 1/2 - 2 1/4)=
3 7/8- 3/20+ 5 (1•4)/(2•4) - 2 (1•2)/(4•2)=
3 7/8 - 3/20+ 5 4/8 - 2 2/8=
8 11/8- 2 2/8- 3/20=
6 9/8- 3/20=
6 (9•5)/(8•5)- (3•2)/(20•2)=
6 45/40- 6/40=
6 39/40
Д)) (2 11/15- 1/3) - (1 5/6- 4/5)=
2 11/15- (1•2)/(3•2) - 1 5/6- (4•3)/(5•3)=
2 11/15- 2/6- 1 5/6- 12/15=
1 26/15- 12/15- 1 7/6=
1 14/15- 1 7/6=
-( 1 (7•5)/(6•5) - 1 (14•2)/(15•2) )=
-( 1 35/30- 1 28/30)= - 7/30