207

a)
$3x-2x\left(1-5x\right)+3$
$3x-2x+10x^2+3$
$10x^2+x+3$
b)
$5\left(6x+10\right)\left(x-2\right)$
$5\cdot\left(6x^2-12x+10x-20\right)$
$30x^2-60x+50x-100$
$30x^2-10x-100$
c)
$z-\left(z-1\right)\left(z-2\right)$
$z-\left(z^2-2z-z+2\right)$
$z-z^2+2z+z-2$
$-z^2+2z-2$
d)
$\left(x+3\right)\left(x+4\right)-x\left(x+1\right)$
$x^2+4x+3x+12-x^2-x$
$6x+12$