Let the money invested by C be Rs.x.
According to the question;
Investment of B= Rs.90/100 * x (given)
Investment of C= Rs.x (assumed)
Investment of A= Rs.110/100 * B (given)
B= Rs.90/100 * x
or, 110/100*90/100*x + 90/100*x + x = 5780
or, 99/100x +90/100x +100/100x = 5780 (solving and taking L.C.M=100)
or, 289/100x = 5780
or, x = 5780*100/289
or, x = Rs. 2000/-
Therefore, C invested Rs.2000.
Hope i helped u:)