a) $\frac{22}{7}:(11-x)+\frac{2}{3}=\frac{7}{5}$
$\frac{22}{7}:(11-x)=\frac{7}{5}-\frac{2}{3}$
$\frac{22}{7}:(11-x)=\frac{11}{15}$
$(11-x)=\frac{22}{7}:\frac{11}{15}$
$11-x=\frac{30}{7}$
$x=\frac{47}{7}$
Vậy: $x=\frac{47}{7}$
b) $(x+1)+(x+2)+(x+3)+...+(x+100)=5550$
`=>`$100x+(1+2+...+100)=5550$
`=>`$x=[5550-(1+2+...+100)]:100$
`=>`$x=(5550-5050):100$
`=>`$x=5$
Vậy: $x=5$