₹12000 is placed in a scheme paying 10% per annum, the interest being compounded annually and simple interest being reckoned for any part of a year. The interest earned in 1 year 6 months (in ₹) is:

After one year the money is $12000\times 1.10$ = ₹13200. The next six months add half a year's interest on that: $13200\times 0.05$ = ₹660, so the amount is ₹13860 and the interest ₹1860. (₹1800 is plain simple interest for 18 months and never compounds the first year; ₹1892 comes from compounding half-yearly at 5% three times, $12000\times 1.$$05^3$ = ₹13891.50, which the question does not say happens.)