Problem Solving (PS) | Train X leaves New York at 1 A.M. and travels east at a speed of x mil

let the speed of train X=10m/hr
It has traveled from 1 am till 5.30am, total of 4.5 hrs
Distance=10*4.5=45 miles
This distance has to be covered by train z in 3.5 hrs(it travels from 2 am to 5.30am)
let the speed of z=s
45=sx3.5=450/35=90/7
Now in answer choice plugin value of speed of train X=10
the correct answer is D=90/7

---