Answer: 
4 mph
Step-by-step explanation : 
Let us call x, the woman speed as she goes uphill 
Now, we know that it took the woman 2 hours to go uphill; therefore, the distance covered is 
4* (x)
shortly afterwards, when the woman returns she is walking at x + 2 mph; therefore, the distance she covers is 
D = 4 (x +2 ) 
Since the uphill and the downhill distances ar the same, we have
4x = 2 (x +2 ) 
4x = 2x + 4 
x = 2 
Hence, going to the hill, the woman speed is 2 miles per goo