Simplify.
9y+11z+7y−4z9y+11z+7y−4z
23yz
16y + 15z
16y + 7z
2y + 7z
9y+11z+7y−4z9y+11z+7y−4z
23yz
16y + 15z
16y + 7z
2y + 7z