a)(`2/5`+`1/2`)`^2`
=(`9/10`)`^2`
=`81/100`
b)(`3/4`-`5/6`)`^2`
=(`-1/12`)`^2`
=`1/444`
c)(`1/2`)`^3`-(`-2/5`)`^2`+l`-3/4`l
=`1/8`-`4/25`+`3/4`
=`25/200`-`32/200`+`150/200`
=`143/200`
d)`(`4^10`.`9^5`)`/`(`8^7`.`3^10`)`
=4^10.(3^2)^5/8^7.3^10
=4^10.3^10/8^7.3^10
=4^10/8^7
=`1048576/2097152`
=`1/2`