Tìm x biết: 4.3^3 - [3^2x + 2(4^2 - 15)] = 10^2 - 12

​Tìm x biết:
a) 4.3^3 – [3^2x + 2(4^2 – 15)] = 10^2 – 12
b) 8[5(3x + 4) – 2.3^2] : 31.2^2 = 64