​ how much is 11x(-3)

Fifth or Sixth Grades and above:

If you are multiplying 11x by -3,

$11x(-3) = 11(-3) \times x(-3) \\ = -33 \times -3x \\ = -33 \times -3 \times x \\ = 99 \times x \\ = 99x$ 

Distributive property of multiplication formula is

$a(b + c) = ab + ac$