Question 927721
ALGEBRA-STYLE:
A (who is {{{a}}} years old) is 10 yrs older than B (who is {{{b}}} years old), so {{{a=b+10}}}
B is 10 yrs younger than C (who is {{{c}}} years old), so
{{{b=c-10}}}<--->{{{c=b+10}}}
D (who is {{{d}}} years old) is 10 yrs older than A, so
{{{d=a+10}}}--->{{{d=(b+10)+10}}}--->{{{d=b+20}}}
E (who is {{{e}}} years old) is ten years younger than D, so
{{{e=d-10}}}--->{{{d=(b+20)-10}}}--->{{{d=b+10}}} .
So, {{{highlight(B)}}} is the youngest,
A, C, and E are all the same age, and 10 years older than B,
and D is 20 years  older than B, and the oldest of them all.
 
You can also do it without algebra, plotting ages on a number line.