Question 95172
720/(X+30)+720/(X-30)=10
[720(X-30)+720(X+30)]/(X+30)(X-30)=10
(720X-21600+720X+21600)/(X^2-900)=10
1440X/(X^2-900)=10 NOW CROSS MULTIPLY
10X^2-9000=1440X
10X^2-1440X-9000=0
X^2-144X-900=0
(X-150)(X+6)=0
X-150=0
X=150 MPH IS THE SPEED OF THE PLANE.
PROOF
720/180+720/120=10
4+6=10
10=10