Step-by-step explanation:
[tex]15 {x}^{2} {y}^{3} \\ = 3 \times 5 \times x \times x \times y \times y \times y \\ \\ - 18 {x}^{3} yz \\ = - 2 \times 3 \times 3 \times x \times x \times x \times y \times z \\ \\ common \: factors = 3 \: x \: x \: y \\ \therefore \: greatest \: common \: factor \\ = 3 \times x \times x \times y \\ = 3 {x}^{2} y[/tex]
