Question

A,B are two points on a given line L.L is the midpoint of the section AB. find the coordinate of point B if the coordinate of A=7 and the coordinate of L=4

Answer 1

B--------L--------A
|---3----|----3----|

7-4= 3

4-3 = 1

so, B = 1

Answer 2

A(7,0), L(4,0)), B(x,0).

x-7 = 2(4-7).
X = 1.