[tex](30t+6):6=30t:6+6:6=\bold{5t+1}\\\\-\dfrac{3a-0,8}{2}=\dfrac{-(3a-0,8)}{2}=\dfrac{-3a+0,8}{2}=\dfrac{-3a}{2}+\dfrac{0,8}{2}=\bold{-1{,}5\,a+0{,}4}\\\\-12\cdot\dfrac{y+7}{-4}=3\cdot\dfrac{y+7}1=3\cdot(y+7)=3\cdot y+3\cdot7=\bold{3y+21}\\\\\dfrac{x-20}{-10}\cdot2=\dfrac{x-20}{-5}\cdot1=\dfrac{x}{-5}-\dfrac{20}{-5}=-\frac15x-(-4)=\bold{-0{,}2\,x+4}[/tex]
