B2:

`a)(-5)/12+(-0,625)-7/12+(-3)/8`

`=-5/12-5/8 -7/12-3/8`

`=(-5/12-7/12)+(-5/8-3/8)`

`=-12/12-8/8`

`=-1-1`

`=-2`

`b)(-6,8) . 7/11  -3,2 -6,8 .  4/11`

`=(-6,8 ) . (7/11+4/11)-3,2`

`=-6,8 . 11 /11 -3,2`

`=-6,8-3,2`

`=-10`

`c)5/9-4/9 : 4/3 . 6/5 +1`

`=5/9 - 4/9 . 3/4 . 6/5 +1`

`=5/9 -2/5 +1`

`=25/45 -18/45 +45/45`

`=52/45`

B3:

`a)(1/2)^5 .  (1/8)^2`

`=1/32 . 1/64`

`=1/2048`

`b) ((-3)^10 . 15^5)/(25^3 . (-9)^5)`

`=(3^10 . 3^5 .5^5)/(5^6 . (-3^10))`

`=-3^5 /5`

`=-243/5`

`c) (-1/3)^3 . (-27)^3 -(3^5 +3^8)/(1+3^3)`

`=1/3^3 . 3^9  -(3^5 . (1+3^3))/(1+3^3)`

`=3^6 -3^5`

`=486`

B4:

`a)A=[(1/4-0,5) . 2 +2 2/3 ] :2`

`=[(1/4-1/2) . 2 +8/3 ] :2`

`=[-1/4  .2 +8/3 ] :2`

`=[-1/2+8/3 ]:2`

`=-13/6 :2`

`=-13/12`

`b)B=(2+1/3-0,4) -(7-3/5 -1 1/3 ) -(1/5 +1 2/3 -5)`

`=2+1/3 -0,4 -7 +3/5 +1+1/3 -1/5 -1 - 2/3 +5`

`=(2-7+5+1-1) +(1/3-2/3+1/3) +(3/5 -1/5)-4/10`

`=2/5 -2/5`

`=0`