0.3X/4 = 0.5/3

Assuming the "X" means the variable "x":
x = 20/9 or 2.2222222222222222222222...
You didn't ask for an explanation, so I didn't give one.

multiply both sides by 12 (the least common multiple of 3 and 4)

. 9 x = 2

x = 2/.9 = 20/9

it says to express my answer as a common answer

Then it'll be 2 2/9.

Do mean to express your answer as a common fraction?

Both Damon and Sheenybeany posted a common fraction as the answer.

ok got it

Thanks then.