Well I think you mean [tex]0.(3456)[/tex], I will try to explain as simple as I can ;p
First I would divide 217 by 4, because we need to find 217th digit in 4 digit repeating decimal:
[tex]217/4=\frac{217}{4}=54\frac{1}{4} [/tex]
[tex]54\frac{1}{4}[/tex] it means that 3456 will be reapeted 54 times untill 217th digit, and [tex]\frac{1}{4}[/tex] means that the 217th digit will be the first of those 4 digits in this decimal, so your answer is:
The 217th number after the decimal point in this repeating decimal will be 3
