First, you want to isolate the term with the x, so you can multiply by 4 on both sides:
(5/6)^x=300/432
(5/6)^x=25/36 *I simplified the fraction*
We know that 5² is 25 and 6² is 36, so (5/6)²=25/36
Therefore, x=2.
OR
We can use logarithms (the inverse of exponents) to solve:
log (base 5/6) (25/36)=x *you would have to plug this into a calculator*
x=2
Depends on what your teacher is asking for but both ways will get you the same answer.