Hej!
a)
-2x • (-3x) • 1/4 =
= 6x² • 1/4 = 6/4x² = 3/2x²
b)
(x + 4) + (2x - 6) =
= x + 4 + 2x - 6 = 3x - 2
Pozdrawiam! - Julka