Answer: 4 cm and 11 cm.
Step-by-step explanation:
1. You can calculate the perimeter of a parallelogram as following:
[tex]P=a+b+c+d[/tex]
Where a+b+c+d are the lenghts of the sides.
By definition the parallelogram has two pairs of parallel sides, therefore:
a=c and b=d
Then, you can calculate the perimeter as following:
 [tex]P=2(a+b)[/tex]
2. Let's call the adjacent side [tex]x[/tex], then the other side is 2x+3.
3. Substitute values  and solve for x:
[tex]30=2(x+2x+3)\\30=2(3x+3)\\30=6x+6\\24=6x\\x=4[/tex]
4. Then the lenghts of the sides are:
[tex]x=4cm\\2x+3=2(4cm)+3=11cm[/tex]
