ok first you need to put like with like so let's separate this, x with x and y with y. 6x+9x -8y+4y. ok let's start with the x 6x+9x=15x now the y. WARNING the 8y is negative so be careful there! -8y+4y=-4y see? your answer is negative four now put them together 15x-4y OR -4y+15x hope this helps:) good luck!
