Answer:
the area of the mat = total area added minus the original area of the water color painting.
length of the mat is:
L = 21 in + 3 in + 3 in because 3 in is added to each side
L = 27 inwidth of the mat is:w = 11 in + 3 in + 3 inw = 17in
Area mat = (27 in x 17 in) - ( 21 in x 27 in)
area mat = 108 sq in is the area of the mat
