Question 315237
Mary, Alan, and their house form a right triangle. 
The legs are the distance from Mary to home and the distance from Alan to home.
The hypotenuse is the distance from Mary to Alan. 
Since it's a right triangle, the Pythagorean theorem applies.
{{{A^2+B^2=H^2}}}
{{{7^2+x^2=(x+1)^2}}}
{{{49+x^2=x^2+2x+1}}}
{{{49=2x+1}}}
{{{2x=48}}}
{{{highlight(x=24)}}}