Question 900117
The 4th time that the 1st bus leaves
will be 3:20 PM plus {{{ 3*12 = 36 }}}
or 3:56 PM
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The 3rd time the 2nd bus leaves
will be 3:20 PM plus {{{ 2*18 = 36 }}}
or 3:56 PM
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So the buses leave together at 3:56 PM