To find the smallest decimal, compare place values from left to right: tens, ones, tenths, hundredths.

Numbers	=	12.009, 19.200, 10.290, 19.009
Compare tens: 1, 1, 1, 1 (all 1). Compare ones: 2, 9, 0, 9. 0 is the smallest, so 10.29 is the smallest number.
Smallest	=	10.29