Explanation
Let d represent the distance left for Alan to hike. Because Alan is four times further from the beginning of the trail than the end, the distance Alan has already completed is 4d.
In symbols:
d+4d=70
To solve for d, first, simplify the left-hand side of the equation by combining like terms.
5d=70
To isolate an unknown value "d", divide both sides by 5.
\(\frac{5d}{5}=\frac{70}{5}d=14\)
Alan still has 14 miles to hike.