Question 1024248
In words:
[ average of ages ] = [ total of ages ] / [ number of individuals ]
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Let {{{ t }}} = total of ages
Average for just the students:
{{{ 17 = t / 25 }}}
{{{ t = 425 }}}
The student's ages total {{{ 425 }}}
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Let {{{ x }}} = the teacher's age
Add in the teacher to same formula:
{{{ 17 + 1 = ( 425 + x ) / ( 25 + 1 ) }}}
{{{ 18 = ( 425 + x ) / 26 }}}
{{{ 425 + x = 468 }}}
{{{ x = 43 }}}
The teacher is 43
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check answer:
{{{ ( 425 + 43 ) / 26 = 18 }}}
{{{ 468 = 26*18 }}}
{{{ 468 = 468 }}}
OK