A prime number is an integer greater than 1 that has no factors other than 1 and itself. Examples of prime numbers include 2, 3, 5, 7, and 11.

A factor is a positive integer that divides evenly into a given number. For example, the factors of 8 are 1, 2, 4, and 8.

Use PEMDAS (Parentheses, Exponents, Multipy/Divide, Add/Subtract):

3 + (4 + 3) ÷ 3 x 4 - 3²
P: 3 + (7) ÷ 3 x 4 - 3²
E: 3 + 7 ÷ 3 x 4 - 9
MD: 3 + \( \frac{7}{3} \) x 4 - 9
MD: 3 + \( \frac{28}{3} \) - 9
AS: \( \frac{9}{3} \) + \( \frac{28}{3} \) - 9
AS: \( \frac{37}{3} \) - 9
AS: \( \frac{37 - 27}{3} \)
\( \frac{10}{3} \)
3\(\frac{1}{3}\)

To subtract these radicals together their radicands must be the same:

3\( \sqrt{28} \) - 6\( \sqrt{7} \)
3\( \sqrt{4 \times 7} \) - 6\( \sqrt{7} \)
3\( \sqrt{2^2 \times 7} \) - 6\( \sqrt{7} \)
(3)(2)\( \sqrt{7} \) - 6\( \sqrt{7} \)
6\( \sqrt{7} \) - 6\( \sqrt{7} \)

Now that the radicands are identical, you can subtract them:

To simplify a radical, factor out the perfect squares:

\( \sqrt{45} \)
\( \sqrt{9 \times 5} \)
\( \sqrt{3^2 \times 5} \)
3\( \sqrt{5} \)