a) $3\frac{1}{10}$ = 3,1 ; $8\frac{2}{10}$ = 8,2 ; $61\frac{9}{10}$ = 61,9
b) $5\frac{72}{100}$ = 5,72 ; $19\frac{25}{100}$ = 19,25 ; $80\frac{5}{100}$ = 80,05
c) $2\frac{625}{1000}$ = 2,625 ; $88\frac{207}{1000}$ = 88,207 ; $70\frac{65}{1000}$ = 70,065