Installment is paid annually and $3$ times. i.e., after first year, second year and third year.
After $3$ years, our original amount $27780$ becomes $27780\times (1.15^3)$ compounding at $15\%$ annually.
Let our installment be $x$. After $2$ year this will be
$x + x \times (1.15)$
After $3$ years, paid amount becomes
$x + x \times (1.15) + x \times (1.15)^2.$
Thus we get
$$27780 \times (1.15)^3 = x + x \times (1.15) + x \times (1.15^2)$$
$\implies x = \frac{27780 \times 1.15^3}{1+1.15+1.15^2} = 12167.$