Answer
The speed of the faster plane is 175 mph.
The speed of the slower plane is 150 mph.
Work Step by Step
Let $x$ mph be the speed of the slower plane.
In 2 hours, the distance travelled by the slower plane is $2x$ miles, while the distance travelled by the faster plane is $2(25 + x)$ miles.
Since one is due North and the other is due South at the same starting time, they are travelling on a straight path opposite to each other. Therefore,
$2x + 2(25 + x) = 650$
$2x + 50 + 2x = 650$
$4x = 600$
$x = 150$
The speed of the faster plane is 150 + 25 = 175 mph.
The speed of the slower plane is 150 mph.
