Not entirely, it could be an isoceles triangle (a triangle which all sides are different lengths) but there is still a possibility.
perimeter = sum of all sides
27 = 9+7.8+x
x (third side) = 10.2
Answer:
Length = 45.37 in
Width = 30.56 in
Step-by-step explanation:
Let the width of the picture be 'w' inches.
Given:
Perimeter of the picture is, 
Length is 15.75 inches shorter than twice the width. So, length is:

Now, we know that the perimeter of a rectangular shape is given as the sum of all of its side. So, the picture is also of rectangular shape and hence the perimeter is given as:

Plug in the values of 'l' and 'P' and solve for 'w'. This gives,

Therefore, the width of the rectangular picture is 30.56 inches.
Length of the picture is, 
So, length of the picture is 45.37 inches and width is 30.56 inches.