`6)5. (-2/5)^2 + 2.(-2/5) + 4.(-2/5)^0`

`=5. 4/25 + (-4)/5 + 4.1`

`=20/25 -4/5 +4`

`=4/5-4/5+4`

`=4`

`7)3. (-2/3)^2 -2.(-2/3) + 4.(-2/3)^0`

`=3. 4/9 +4/3 + 4.1`

`=12/9 + 4/3 +4`

`=8/3 +4`

`=20/3`

`8)9.(2/3)^2 +2.(-9/2) +4.(-15/7)^0`

`=9. 4/9 + (-18)/2 + 4.1`

`=4-9+4`

`=-1`

`9) (2/3)^3 - 4.(-1 3/4)^2 + (-2/3)^3`

`=(2/3)^3 + (-2/3)^3 - 4.( -7/4)^2`

`=0- 4. 49/16`

`=0- 49/4`

`=-49/4`

`10)(-1/3)^(-1) - (-6/7)^0 + (1/2)^2 :2`

`=-3 - 1 + 1/4 :2`

`=-4 + 1/8`

`=-31/8`