the answer is 19
work :
1-multiply the numbers by a submultiple of 10 to remove the decimal points.
[tex]17.1 \times 10 = 171 \\ \\ 0.9 \times 10 = 9[/tex]
2-
now do the division :
[tex]171 \div 9 = 19[/tex]
so the answer is 19
note: there is no need to get it back to decimal number unless you multiply just one of the numbers or multiply the numbers with different submultiples of 10
good luck