`a)`
`(5x^3 - 7x^2 + x) : 3xn`
` = 5x^3 : 3xn - 7x^2 : 3xn + x : 3xn`
` = 5/3 x^2n - 7/3 xn + 1/3n`
`b)`
`(13x^4 y^3 - 5x^3y^3 + 6x^2y^2) : 5 x^n y^n`
` = 13 x^4 y^3 : 5 x^n y^n - 5 x^3 y^3 : 5 x^n y^n + 6 x^2 y^2 : 5 x^n y^n`
` = 13/5 x^{4-n} y^{3-n} - x^{3-n} y^{3-n} + 6/5 x^{2-n} y^{2-n}`