x+y = 4
x=4-y
52x+50y=204
52(4-y)+50y=204
208-52y+50y=204
208-2y=204
-2y=-4
y=2
x= 4-2=2
check 52*2=104
50*2 = 100
104+100=204
so he traveled 2 hours at both 50 and 52 mph
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