The sum of the speeds of two trains is 725.2 miles per hour. if the speed of the first train is 10.8 mph faster than the second train, find the speed of each.

X=first train speed
y=second train speed

sum of speeds is 725.2
x+y=725.2

x is 10.8 more than y
x=10.8+y

subsitute 10.8+y for x

10.8+y+y=725.2
10.8+2y=725.2
minus 10.8 from both sides
2y=714.4
divide both sides by 2
y=357.2
x=10.8+y
x=10.8+375.2
x=386

the speed of first train is 386mph
second train is 357.2mph

Your answer 
1st. train speed is 286,
2nd train speed is 357.3

7/12 is the ¡!