Step-by-step explanation:
[tex]15x {}^{2} y {}^{3} = 3 \times 5 \times x \times x \times y \times y \times y \\ \\ -20x {}^{3} yz = - 2 \times 2 \times 5 \times x \times x \times x \times y \times z[/tex]
[tex]GCF = 5 {x} y = 5 \times x \times y[/tex]
