Question 1129966
{{{x}}}= Tina's age     19
{{{x+9}}}= Jack's age, because "Jack is nine years older than Tina."
{{{(x+9)-18=x-9}}}= Ali's age, because "Ali is eighteen years  younger  than Jack."
{{{(x-9)-3=x-12}}}= how hold Ali was the years ago
{{{4(x-12)=4x-48}}}= Jack's age, because "Jack is four times as old as  Ali was three year ago."
We see that Jack's age is {{{x+9}}} and {{{4x-48}}} , so
{{{4x-48=x+9}}} is our equation.
Adding {{{-x+48}}} to both sides of the equation,
{{{4x-48-x+48=x+9-x+48}}} ,
and "collecting like terms" and simplifying, we get
{{{3x=57}}}
Dividing both sides of the equation by 3, we get
{{{3x/3=57/3}}} , which simplifies to
{{{highlight(x=19)}}} .
 
So, Tina is {{{highlight(19)}}} ;
Jack is {{{19+9=28}}} ;
Ali is {{{28-18=10}}} ;
3 years ago Ali was {{{10-3=7}}} ,
and Jacks age is four times as much as that: {{{4*7=28}}} .