Question 971041
dos posibilidades

y = log base 10 [3*(x-1)]
x= log base 10 [3*(y-1)]

10^x =3y-3
3y=10^x  + 3
y =[ (10^x+3)]/3

o 

y=log base 3 (x-1)  no sé  si 3 es base 
x=log base 3 (y-1)
3^x=y-1
1+3^x=y