maths - indices

1.3(3^x)-3^(x-1)=216
9(3^(x-1))-3^(x-1)=216
8(3^(x-1))=216
(3^(x-1))=27
(3^(x-1))=3^3
x-1=3
x=4

2. 4^(2x)=16(2^x)
2^(4x)=(2^4)(2^x)
2^(4x)=(2^(4+x))
4x=4+x
3x=4
x=4/3

3.2^3x=8(4^x)
2^(3x)=(2^3)(2^(2x))
2^(3x)=(2^(2x+3))
3x=2x+3
x=3