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x + y = 250 (1) (x = the distance traveled at 60 mph)
= (2) (he spent twice as much time traveling at the faster speed)
x + y = 250 (1')
140x - 60y = 0 (2')
Multiply eq(1') by 60 (both sides). You will get
60x + 60y = 250*60
140x - 60y = 0
-------------------------------Add the equations
200x = 250*60 ====> 2x = 25*6 ====> x = 25*3 = 75.
Answer. 75 miles at the rate of 60 mph and the rest 250 - 75 = 175 miles at the rate 70 mph.
Check. = 1.25 hours. = 2.5 hours = 2 times 1.25 hours. ! Correct !
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The solution by the other tutor is INCORRECT.