[tex]\displaystyle a). (2x-3)\cdot6=54-6x. \\ 12x-18=54-6x \\ 12x+6x=54+18 \\ 18x=72 \\ x= \frac{72}{18} \\ x=4 \\ b).512:(9x-19)-4=120:2 \\ 512:(9x-19)-4=60 \\ 512:(9x-19)=60+4 \\ 512:(9x-19)=64 \\ 9x-19=512:64 \\ 9x-19=8 \\ 9x=8+19 \\ 9x=27 \\ x= \frac{27}{9} \\ x=3[/tex]
