Let $A=\left\{3,6,12,15,18,21\right\}, B=\left\{4,8,12,16,20\right\}, C=\left\{2,4,6,8,10,12,14,16\right\}$ and $D=\left\{5,10,15,20\right\}$. Find: $C-A$

Let $A=\left\{3,6,12,15,18,21\right\}, B=\left\{4,8,12,16,20\right\}, C=\left\{2,4,6,8,10,12,14,16\right\}$ and $D=\left\{5,10,15,20\right\}$. Find: $D-A$

Let $A=\left\{3,6,12,15,18,21\right\}, B=\left\{4,8,12,16,20\right\}, C=\left\{2,4,6,8,10,12,14,16\right\}$ and $D=\left\{5,10,15,20\right\}$. Find: $B-C$

Let $A=\left\{3,6,12,15,18,21\right\}, B=\left\{4,8,12,16,20\right\}, C=\left\{2,4,6,8,10,12,14,16\right\}$ and $D=\left\{5,10,15,20\right\}$. Find: $B-D$

Let $U=\left\{1,2,3,4,5,6,7,8,9\right\}, A=\left\{1,2,3,4\right\}, B=\left\{2,4,6,8\right\}$ and $C=\left\{3,4,5,6\right\}$. Find : $A^{\text{'}}$

Let $U=\left\{1,2,3,4,5,6,7,8,9\right\}, A=\left\{1,2,3,4\right\}, B=\left\{2,4,6,8\right\}$ and $C=\left\{3,4,5,6\right\}$. Find : $B^{\text{'}}$

Let $U=\left\{1,2,3,4,5,6,7,8,9\right\}, A=\left\{1,2,3,4\right\}, B=\left\{2,4,6,8\right\}$ and $C=\left\{3,4,5,6\right\}$. Find : ${\left(A\cap C\right)}^{\text{'}}$

Let $U=\left\{1,2,3,4,5,6,7,8,9\right\}, A=\left\{1,2,3,4\right\}, B=\left\{2,4,6,8\right\}$ and $C=\left\{3,4,5,6\right\}$. Find : ${\left(A\cup B\right)}^{\text{'}}$

Let $U=\left\{1,2,3,4,5,6,7,8,9\right\}, A=\left\{1,2,3,4\right\}, B=\left\{2,4,6,8\right\}$ and $C=\left\{3,4,5,6\right\}$. If ${\left(A^{\text{'}}\right)}^{\text{'}}=\left\{a, b, c, d\right\}$, then find the value of $\left(a+b+c+d\right)$.