Concept:Use the difference of squares formula a2−b2=(a−b)(a+b) and factorisation by grouping.Explanation:First, factor the numerator.y2−121=(y−11)(y+11)64−x2=(8−x)(8+x)So numerator becomes (y−11)(y+11)(8−x)(8+x).Now factor the denominator: 8y+xy+88+11x.Group terms: (8y+88)+(xy+11x)=8(y+11)+x(y+11)=(y+11)(8+x).Cancel the common factors (y+11) and (8+x) from numerator and denominator.The expression simplifies to (y−11)(8−x).Answer:Option C: (y−11)(8−x)