Evaluate

To multiply algebraic expressions, we use commutative and associative laws along with the laws of indices, i.e., $a^{m} \times a^{n}=a^{m+n}$.

We have:

$\left(-8 x^{2} y^{6}\right) \times(-20 x y)$

$=\{(-8) \times(-20)\} \times\left(x^{2} \times x\right) \times\left(y^{6} \times y\right)$

$=\{(-8) \times(-20)\} \times\left(x^{2+1}\right) \times\left(y^{6+1}\right)$

$=160 x^{3} y^{7}$

$\therefore\left(-8 x^{2} y^{6}\right) \times(-20 x y)=160 x^{3} y^{7}$

Substituting x = 2.5 and y = 1 in the result, we get:

$160 x^{3} y^{7}$

$=160(2.5)^{3}(1)^{7}$

$=160 \times 15.625$

$=2500$

Thus, the answer is 2500 .