Question 1135784
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(1) Algebraically....<br>
Let x be her son's age
Then x+18 = her age<br>
One year ago, their ages were
son: x-1
her: x+17<br>
Her age 1 year ago was three times his age then:<br>
{{{x+17 = 3(x-1)}}}
{{{x+17 = 3x-3}}}
{{{20 = 2x}}}
{{{x = 10}}}<br>
Her son's age is x=10; her age is x+18 = 28.<br>
CHECK: 10-1 = 9; 28-1 = 27; 27 = 3*9<br>
(2) informally, using logical reasoning and a bit of mental arithmetic....<br>
The difference between their ages is 18 years; when she was three times as old as her son, the difference between their ages was twice her son's age.  So at that time her son's age had to be 9, which means she was 27.  That was 1 year ago; so now they are 10 and 28.