Question 1154094


let Mary ‘s age be {{{x}}} and Justin’s age {{{y}}}

if Mary is less than {{{15}}} years old, we have

{{{x<15}}}....1)


 if she is {{{half}}} as old as Justin, we have

{{{x=y/2}}}.....2)


if in {{{11}}} years she will be {{{2/3}}} years old as Justin, we have


{{{x+11=(2/3)(y+11)}}}

{{{x+11=2y/3+22/3}}}

{{{x=2y/3+22/3-11}}}

{{{x=2y/3+22/3-33/3}}}

{{{x=2y/3-11/3}}}......3)


from 2) and 3) we have


{{{y/2=2y/3-11/3}}}

{{{y/2-2y/3=-11/3}}}

{{{3y/6-4y/6=-11/3}}}

{{{-y/6=-11/3}}}

{{{-y=-(11/3)6}}}

{{{-y=-11*2}}}.......both sides multiply by {{{-1}}}

{{{y=22}}}


 Justin is {{{22}}} years old


check if if Mary is less than {{{15}}} years old

{{{x=y/2}}}.....2).....substitute {{{y}}}

{{{x=22/2}}}

{{{x=11}}}-> true, because {{{11<15}}}