A rectangle has sides of 3x – 4 and 7x + 10. Find the expression that represents its perimeter.

3x-4+7x+10=
3x+7x=10x
−4+10= 14
10x+14
that is my answer please help

You just added two sides, a rectangle has four sides. So the perimeter should be twice what you calculated. However, you have several errors.

-4+10=-6

So you should have gotten 10x-6, however, that needs to be doubled (you only added two sides).