1) (6abc^2) / 15a^2 x (2bc / 3a)^-2 =
2) (4x^3 2x^-4) / (5x)^-1 =
minus powers swap between top and bottom in fractions. So, if you want all positive exponents,
(6abc^2) / 15a^2 * (2bc / 3a)^-2
= (6abc^2) / 15a^2 * (3a / 2bc)^2
= (6abc^2 * 3a)/(15a^2 * 2bc)
= 18a^2bc^2 / 30a^2bc
= 3c/5
try the other one the same way. We can check your work.