Question

Simply the product -7x/5y * 5x/-7

Answer 1

-7x/5y * 5x/-7
= x^2/y

(-) times(-) = positive
and canceled out 7, 5 
so answer is
x^2/y

Answer 2

We are asked to simplify the expression $\frac{-7x}{5y} \cdot \frac{5x}{-7}$, 

what we do is, we form a single fraction where the numerator is the product of the numerators, and the denominator is the product of the denominators, that is:

$\frac{-7x}{5y} \cdot \frac{5x}{-7}= \frac{-7\cdot5 \cdot x \cdot x}{5 \cdot(-7) \cdot y}$

simplify the common numbers and terms in the numerator and denominator:

$\frac{-7\cdot5 \cdot x \cdot x}{5 \cdot(-7) \cdot y}=\frac{5 \cdot x \cdot x}{5 \cdot y}=\frac{x \cdot x}{y}= \frac{ x^{2} }{y}$


Answer: $\frac{ x^{2} }{y}$