Consider the situtaion shown in figure. Find distance of image of O from eye E.

Explanation

Shift by (1), `t_(1)(1-1//mu_(1))=3(1-2//3)=1cm`
Shift by (2), `t_(2)(1-1//mu_(2))=4(1-4)=3cm`
Shift by (3), `t_(3)(1-1//mu_(3))=6(1-1//3)=4 cm`
Image of O is formed at I.
OI=8 cm `rArrEO=6+6+1+4+1+3+6=27 cm`
EI=EO-OI=27-8=19 cm