The corner where Starbucks is located could be considered to be the right angle in a right triangle having legs of 8 miles (distance to you) and 7 miles (distance to your friend). The straight-line distance (d) from you to your friend is the hypotenuse of that triangle. Its length can be found from the Pythagorean theorem.
d² = 8² +7²
d² = 64 +49 = 113
d = √113 ≈ 10.6
You and your friend are about 10.6 miles from each other.
