Distance problem quant

GRE Quant Problem Solving
1

I have attached the doubt with this email.
My question is if x is moving 50% faster then that means x will travel 40 miles and in that time y will travel 20 miles. So, after y takes another 20 miles, x will cover the distance of y with a total of 80 miles in 8/3 hours as given. So, why can’t we calculate the speed of y using the following:
d=rt
40=r*8/3
r= 15

Please reply
doubt

2

50% faster means car X is going 1.5 times the speed of car Y. So when X travels 40 miles y will travel 40/1.5=26.66 miles. So after two more 26.66 miles, they would catch up after covering 120 miles (X would cover 120, Y would cover 80 to catch up) in 8/3 hours. So d=rt
80=r*8/3
r=30 miles/hour