17)2^x=t, t>0
t^2-3t +2=0,
D=1
t1=2, 2^x=2,x=1;
t2=1, 2^x=2^0,x=0;
++++++++++++++
16) 6^(12x+3) = 6^2(x-4)
12x+3=2x-8
x= -11/10
x=-1,1
++++++++++++++++++++
15) -4x-1= 2x,
6x=-1
x=-1/6
++++++++++++++++++
14)2x-9=x+8,
x= 17;
+++++++++++++++++
13) 6-3x=-1
3x=7,
x= 7/3=2 1/3
+++++++++++++++
12) 2 ^3(2x-7) = 2^4,
3(2x-7) = 4
6x-21=4
6x=25,
x= 25/6= 4 1/6.