Mình xin giải như sau:
a)15x-57=3^14:3^9
15.x-57=3^5
15.x-57=243
15.x=243+57
15.x=300
x=300:15
x=20
b)50-[70:(x-1)]=15
70:(x-1)=50-15
70:(x-1)=35
x-1=70:35
x-1=2
x=2+1
x=3
c) (5^2+2^3).x+4^2=7^2
(25+8).x+16=49
33.x=49-16
33.x=33
x=33:33
x=1
d) 2^x:2^5=1
2^x=1.2^5
2^x=2^5
Suy ra x=5
18-(x-2)^5=2.3^2
18-(x-2)^5=2.9
18-(x-2)^5=18
(x-2)^5=18-18
(x-2)^5=0
x=0+2
x=2