What is equivalent to 3x-4-(5x+7)

Easy, so here’s what you do, take care of the parenthesis so it looks like 3x-4 because the negative is disturbed to make the positive 5x a negative and the positive 7x into a negative, a good pointer is anytime you’re multiplying two signs, a good thing to know is if the signs are different, it’s negative, if they’re the same, they’re positive. Now you want to move the negative 5x to the left of the +3x so you should see -5x+3x-4-7 so from here, you want to add the -5x to the 3x to get you -2x so now you should have -2x-4-7 then subtract the 4 from the seven or the seven from the four looking like 4-7 to get you -11 so now you should have
-2x -11 << I hope this helped!! ^_^

Maybe the answer is 20mm. all i really did was just multiply, which is obvious.