a)
[tex]3\left(2x-1\right)+4\left(1-x\right)\\= 6x-3+4-4x\\= 2x+1\\[/tex]
b)
[tex]2\left(7x+5\right)-6\left(x-2\right)\\=14x+10-6x+12\\=8x+22\\[/tex]
c)
[tex]-2x\left(8-x\right)-5\left(x^2+3x\right)\\=-16x+2x^2-5x^2-15x\\=-3x^2-31x\\[/tex]
d)
[tex]5\left(3-2x\right)-\left(4x+6\right)\cdot 3\\=15-10x-12x-18\\=-22x-3\\[/tex]