If we're asking what is the LCD for these fractions? then:
10y^2 = 2 * 5 * y * y
5y^6 = 5 * y * y * y * y * y * y
The LCD is like a parts list with enough parts to make 10y^2 or 5y^6. In this case the parts list is 2 * 5 * y * y * y * y * y * y because that list has enough parts to make 10y^2 or 5y^2.
2 * 5 * y * y * y * y * y * y = 10y^6
Answer: The LCD of 7/10y^2 and x/5y^6 is 10y^6.