Question 134045
Let the windspeed = w and airspeed be a. 
We know distance = speed/time. The distance is the same going both ways
With the wind, the speed is a+w. The time is 4-1=3
Against the wind, the speed is a-w. The time is 4

Given:
{{{1800 = (a-w)* 4}}} --> {{{450 = a -w }}} --> {{{450 +w = a}}}
{{{1800 = (a+w)* 3}}}
{{{600 = a + w}}}
{{{600 = (450 + w) + w }}}  using the value from the first equation above
{{{150 = 2 w}}}
{{{ 75 = w}}}

That makes airspeed = 525

Check your answer. Is 1800/(525-75) = 4? yes it is. check