Can somebody explain to me how to do number 7? !

7) Factor 3x² - 12

So, look at those 2 numbers, and see what they both have in common.

They are both divisible by 3! So, basically you divide 3x² and -12 with 3.

3(x² - 4)

It would be factorized like that because if you multiply 3 by x², you would get 3x², and if you multiplied 3 with -4, you would get -4.

~Hope I helped!~