10. A garden is to be surrounded by a paved
 border of uniform width.
 16 m
 |-X-
 L=16+X+x
 L= 2x+16
 W=14+x+x
 W= 2x+14
 14 m
 a) Write a simplified expression for the
 area of the border.
 b) The border is to have an area of
 216 m². Find the width of the border.