Simplify the following monomials. Your answer should contain positive exponents only.
18) 7a^5b^6c/14a^5b^9
19) -9xy^5z^3/36xy^4z^5
20) -15r^6s^7t^4/3r^2s^9t^7
as written :18) 7a^5b^6c/14a^5b^9 = (1/2)a^10 b^15 c
if property written as
18) 7a^5b^6c/(14a^5b^9) = c/(2 b^3)
the other two are wrong as well
18) a^5b^-3c
19) -3xy^1z^-2
20) -5r^4s^-2t^-3