Find (2+3i)-(-5+8i)
also
Find (5-9i)(2+3i)
When adding or subtracting complex numbers add/subtract the real component and the imaginary component separately
$\displaystyle (a+bi)-(c+di) = (a-c) + (b-d)i$
When multiplying treat it the same as you would with any polynomial. Just recall that $\displaystyle i^2 = -1$