Answer
$(3x-1)$
Work Step by Step
In order to match the first term of the dividend, $3x^2$, the divisor $(x-3)$ must be multiplied by $3x$. The $3x$ will go on top of your division sign.
$$(3x)(x-3) = 3x^2-9x$$
Then, subtract this from the first two terms of the dividend.
$$(3x^2-10x+3) - (3x^2 - 9x) = -x$$
Bring down the next term of the dividend.
$$-x+3$$
Multiply the divisor by $(-1)$ to match this. The $-1$ will follow the $3x$ on top of your division sign.
$$(-1)(x-3) = (-x+3)$$
Subtract this from the dividend. Since this results in zero, you have no remainder and a final answer of $(3x-1)$