To simplify the expression (4x - 3(x - 2)21), first distribute (-3) into ((x - 2)):
[ -3(x - 2) = -3x + 6. ]
Now, substitute this back into the expression:
[ 4x - 3x \cdot 21 + 6 \cdot 21. ]
This yields:
[ 4x - 63x + 126 = -59x + 126. ]
So, the simplified expression is (-59x + 126).