The relation is 5x+10y=90
Because If she hiked the 5-mile trail x times, she would have walked 5x miles in total.
Likewise, if she hiked the 10-mile trail y times, she would have walked 10y miles as she did so. Since we know the total of her walking was 90 miles, we can write the above equation, linking together the information.
Without additional information about x and y (such as being told she went hiking 12 times in all, for example) we cannot come to a definite statement about the values of x and y
