Multiplying terms within a bracket by the term in front. This process is the reverse of Basic factorising
e.g. $3(x+2)=3x+6$
You multiply everything inside the brackets by the term in front of the brackets. In the above case, $x$ is multiplied by 3 as is 2.
$2x(3x-4)=6x^2-8x$
Students often get caught out if there is a minus sign in front:
$-3(x-4)=-3x+12$
Especially if it's in the middle of an expression:
$2(x+3)-4(x-5)=2x+6-4x+20$
The final '+20' is missed a significant number of times!
