x3y+4x2y2+3xy3+7x2y2+3x3+4y2+6xy+7x3y+8y2 is the given expression.
Now, x3y and 7x3y are like terms.
Hence they can be added to give 8x3y. [0.5 Mark]
Similarly, 4x2y2 and 7x2y2 are like terms.
They can be added to give 11x2y2. [0.5 Mark]
Also, 4y2 and 8y2 are like terms.
They can be added to give 12y2. [0.5 Mark]
Thus, the final simplified expression is
8x3y+11x2y2+3xy3+3x3+12y2+6xy. [0.5 Mark]