x + 2i + 15i6 y = 7x + i3(y + 4)
x + 2i + 15(i2)3 y = 7x + i3(y + 4)
x + 2i + 15(-1)3 y = 7x – i(y + 4) ……[∵ i2 = -1, i3 = -i]
x + 2i – 15y – 7x + iy + 4i = 0
(-6x – 15y) + i(y + 6) = 0 + 0i
Equating real and imaginary parts, we get
-6x – 15y = 0 and y + 6 = 0
-6x – 15y = 0 and y = -6
-6x – 15(-6) = 0
-6x + 90 = 0
∴ x = 15
∴ x + y = 15 – 6 = 9