Question 1146613


 my sister is {{{8}}} years older than I am : 

{{{sister= I+8}}}....eq.1 


The sum of our ages is {{{38}}}:

{{{sister+I=38}}}....eq.2


substitute {{{sister}}} with {{{I+8}}} from eq.1 


{{{I+8+I=38}}}....eq.2......solve for {{{I}}}

{{{2I=38-8}}}

{{{2I=30}}}

{{{I=15}}}

now calculate {{{sister= I+8}}}

{{{sister= 15+8}}}

{{{sister= 23}}}


so, I am {{{15}}} years old and my sister is {{{23}}} years old