1. The monomials are:
[tex]15 {x}^{4} {y}^{6} = 3 \times 5 {x}^{4} {y}^{6} [/tex]
and
[tex]6 {x}^{5} {y} = 2 \times 3 {x}^{5} y[/tex]
The highest common factor is the product of the least powers of the common factors.
The HCF is
[tex]3 {x}^{4} y[/tex]
2. The monomials are:
[tex]12 {x}^{3} = {2}^{2} \times 3 {x}^{3}[/tex]
[tex]4 = {2}^{2} [/tex]
The HCF is
[tex]{2}^{2} = 4[/tex]
