Well think about it, the key words there are more than and less than so if he traveled let's say from his house until the first city that's 100 miles for the first one and then they say that he traveled 10 miles less than the distance from the first city until the second city. The total distance is 280 because if you read the very last sentence it says that from the original distance from the first city is about 100 miles and then it says if the the distance from the second city to the third city was the same that means that the equation goes like this: (90*2)+100 and in order to get this correctly you must do P.E.M.D.A.S which is parenthesis, exponents, multiplying, dividing, adding and subtracting so there you go.
+150 
