a)

$5,23+4,21=9,44$

$12-2,09=9,91$

$10\cdot 57,08=570,8$

$3\cdot 11,2=33,6$

$6,28:100=0,0628$

$50,55:5=10,11$

b)

$4,5+27,89+5,5=32,39+5,5=37,89$

$20-\left(2,5+7,6\right)=20-10,1=9,9$

$40\cdot 2,1=84$

$5,22:0,1=5,22\cdot 10=52,2$

$4,64:0,02=464:2=232$