What is the value of x in the equation 2 to the 12 = 2to the 15x?

2^12=2^(15x)
If the bases are equal, the exponents must be equal too:
12=15x
Solving for x. Dividing both sides of the equation by 15:
12/15=15x/15
Simplifying. Dividing the numerator and the denominator on the right side of the equation by 3:
(12/3)/(15/3)=x
4/5=x
x=4/5

The value of x is 4/5

Yes, 1/3 is a rational number. The decimal is not though.