So first you want to do the multiplication.
(3-4i)*(1+5i)
So what you want to do is multiply everything inside the parenthesis by everything inside the other parenthesis.
Or,
3 * 1 + 3 * 5i + -4i * 1 + (-4i) * 5i
Or,
3 + 15i + -4i - 20i
Then,
3 + -9i
3 - 9i - (2 - i)
Open the parenthesis, and since it has a minus before it reverse the operator inside of the parenthesis.
3 - 9i - 2 + i
Or,
1 - 8i
