Question 1157652
Let the dog's age = {{{ x }}}
{{{ 3x }}} = Phylis's age
given:
{{{ 3x + x = 42 }}}
{{{ 4x = 42 }}}
{{{ x = 21/2 }}}
{{{ x = 10.5 }}}
and 
{{{ 3x = 31.5 }}}
The dog is 10.5 yrs old
Phylis is 31.5 yrs old
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check:
{{{ 4x = 42 }}}
{{{ 4*10.5 = 42 }}}
{{{ 42 = 42 }}}
OK