Draw AE, DF parallel to x-axis.
Draw BE, CF parallel to y-axis.
In right triangles Δ ABE, Δ DCF
AB = DC, ∠BAE = ∠CDF
∠ABE = ∠DCF
∴ AE = DF= 6 – 2 = 4
BE = CF = 5 – 3 = 2
x coordinate of C = 4 + DF = 4 + 4 = 8
y coordinate of C = 7 + CF = 7 + 2 = 9
Coordinates ofC (8, 9)