4y - 9 = 3
add 9 to both sides
4y = 12
divide both sides by 4 so 4 divided by 4 is one and 12 divided by 4 is 3 thus getting your answer of 3
y=3
I switched both sides of the equation in the very beginning so it would be easier to solve.
The answer to the question is as the following.
3.643 * 10^(-1)