To solve this problem you must apply the proccedure shown below:
1. By definition, the opposite sides of a parallelogram are parallel and have equal length.
2. The figure attached shows that the opposite sides with equal length are:
[tex]a=c\\b=d[/tex]
3. Keeping this on mind, you have that the side c and a are equal and measure six centimeters.
4. To find the length of the other sides, you must apply the following formula for calculate the perimeter of a parallelogram:
[tex]P=2(a+b)[/tex]
4. If you solve for b, you will obtain the measure of b and d:
[tex]30cm=2(6cm+b)\\30cm=12cm+2b\\b=9cm[/tex]
Therefore the answer is:
The lengths of the sides are: 6 cm, 6 cm, 9 cm and 9 cm.
