Question 254254
If we assume that the dining room and living room are all in one room, then we can say
LxW = 300
which is 
L x W - 300 = 0
If we cannot assume this then
L1 x W1 = dining room area
L2 x W2 = living room area
together they equal 
L1 X W1 + L2 x W2 = 300
or
L1 X W1 + L2 x W2 - 300 = 0
I hope its the first option.