Question 840566
perimeter P = 2w + 2l where w = width and l = length

we are told that the length is twice as long as it is wide which said differently means its 2 times the width

we can thus write the perimeter P as P = 2w + 2(2w)
so lets solve for w; 30 = 2(w) + 4(w); 30 = 6(w) hence w = 5 therefore l will 2*5 = 10

now to find the area with is w * l = 5 * 10 = 50 cm2