Question 301797
Let {{{h}}} = speed of helicopter with no wind
 {{{6}}} = speed of wind
given:
with the wind:
{{{720 = (h + 6)*t}}}
against the wind:
{{{630 = (h - 6)*t}}}
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This is 2 equations with 2 unknowns
solve for {{{h}}} and {{{t}}}