<PRE><B>Question 77448</B>
Distance (d)= rate(r) times time (t) or d=rt; t=d/r 

Let x=rate of speed of wind

Speed of plane with wind =180+x
Distance travelled with wind is 7 mi
Time to travel 7 mi with wind is 7/(180+x)-----Time #1
Speed of plane against wind=180-x
Distance travelled against wind is 5 mi
Time to travel 5 mi against wind is 5/(180-x)----Time #2

Now we are told that Time #1 = Time #2  so our equation to solve is:

7/(180+x)=5/(180-x)  Multiply both sides by (180+x)(180-x) to get rid of the fractions:

7(180+x)(180-x)/(180+x)=5(180+x)(180-x)/(180-x) Simplify by cancelling

7(180-x)=5(180+x)  get rid of parens
1260-7x=900+5x  subtract 1260 and also 5x from both sides

1260-1260-7x-5x=900-1260+5x-5x  collect like terms

-12x=-360  divide both sides by -12

x=30 mph--------------------speed of the wind

CK 
 t=d/r
7/(180+30)=5/(180-30)
7/210=5/150
1/30=1/30

Hope this helps----ptaylor

</PRE>