assuming that the paper is a rectangle you know that it would have two equal sides. So, if you have a width of 8 and a length of x. to figure out the problem you would multiply the 8 by 2 since you have two sides that measure 8 cm. this would give you 16. You would then subtract the 16 from the 38 which gives you 22. You then divide the 22 by 2 to find the length of he paper.
8x2=16
38-16=22
22/2=11 which is your final answer