Question 480518
Now Michael is 16, he is  twice as old as his sister, so his sister now is {{{16/2=8}}} years old.
Let x years ago Michael was three times as old as his sister, Mickael's age x years ago was {{{(16-x)}}}, his sister age was {{{(8-x)}}}
{{{(16-x)/3=8-x}}}multiply by 3
{{{16-x=3(8-x)}}}
{{{16-x=24-3x}}}
{{{-x+3x=24-16}}}
{{{2x=8}}}
{{{x=4}}} years ago Michael was three times as old as his sister