Question 579001
{{{-(12y)/(7x)}}}•{{{21x^5y^2}}} 
cancel the 7 into 21
{{{-(12y)/x}}}•{{{3x^5y^2}}}
divide the x into x^5, subtract exponents 
(-12y) * {{{3x^((5-1))y^2}}}
(-12y) * {{{3x^4y^2}}}  
multiply like terms, add the exponents of y
{{{-36x^4y^((2+1))}}} = {{{-36x^4y^3}}}