Simplify the expression below -3(10x + 4y) + 6(6x − 2y)

You need to expand the brackets before you can simplify, so:
-3 × 10x = -30x
-3 × 4y = -12y

6 × 6x = 36x
6 × -2y = -12y

So now you have (-30x - 12y) + (36x - 12y)
-30x + 36x = 6x
-12y + -12y = -24y
So your answer is 6x - 24y. I hope this helps!