2^x+2^(x-3)=18
2^(x-3)*(2^(x-x+3)+1)=18
2^(x-3)*(2^3+1)=18
2^(x-3)*9=18
2^(x-3)=2
2^(x-3)=2^1
x-3=1
x=3+1
x=4
2^x+2^(x-3)=18
2^(x-3)*(2^(x-x+3)+1)=18
2^(x-3)*(2^3+1)=18
2^(x-3)*9=18
2^(x-3)=2
2^(x-3)=2^1
x-3=1
x=3+1
x=4