Since
1. the 18 cm. side of the first quadrilateral corresponds to the
36 cm. side of the second quadrilateral.
2. the quadrilaterals are similar.
3. 18 cm is one-half of 36 cm and 36 cm is twice 18 cm,
therefore
every side of the first quadrilateral is half the side of the
corresponding side of the second quadrilateral.
and
every side of the second quadrilateral is twice the side of the
corresponding side of the first quadrilateral.
So:
I. The side of the second quadrilateral that measures b cm. corresponds
to the side of the first quadrilateral that measures 6 cm., so b is
twice 6 cm. or 12 cm. Answer: b = 12.
II. The side of the second quadrilateral that measures c cm. corresponds
to the side of the first quadrilateral that measures 10 cm., so c is
twice 10 cm. or 20 cm. Answer: c = 20.
III. The side of the second quadrilateral that measures 48 cm. corresponds
to the side of the first quadrilateral that measures a cm., so a is
half of 48 cm. or 24 cm. Answer: a = 24
Edwin