Question 1044736
let Todd's age be {{{x}}}
if Mary is twice as old as Todd, than Mary's age is {{{2x}}} 

in {{{8}}} years, Todd's age will be {{{x+8}}} and Mary's age will be {{{(2x+8)}}} 

if their ages will total {{{70}}}, than

 {{{(x+8)+(2x+8)=70}}}

 {{{x+8+2x+8=70}}}

{{{3x+16=70}}}

{{{3x=70-16}}}

{{{3x=54}}}

{{{x=54/3}}}

{{{x=18}}}-> Todd's age
 {{{2x=2*18=36}}} Mary's age 

check:

 their age in {{{8}}} from now will be: 
{{{x+8=18+8=26}}}-> Todd's age
{{{2x+8=2*18+8=36+8=44}}} Mary's age

and their sum must be {{{70}}}: {{{26+44=70}}} which is true