Question 890373
If {{{ t }}} = number of teams, they can wash
{{{ 5t }}} cars in 1 hour
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If {{{ t = 3 }}}, they can wash 
{{{ 5*3 = 15 }}} cars in 1 hour
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In 7 hours, they can wash 7 times that many cars
{{{ 7*15 = 105 }}}
3 teams can wash 105 cars in 7 hours