Answer & Step-by-step explanation:
[tex]1)\\(3x+9)+(2x+4)\qquad\text{combine like terms}\\\\=(3x+2x)+(9+4)\\\\=\boxed{5x+13}\\\\===========================[/tex]
[tex]2)\\(2n+6)+(6n-2)\qquad\text{combine like terms}\\\\=(2n+6n)+(6-2)\\\\=\boxed{8n+4}\\\\===========================[/tex]
[tex]3)\\(-3x+9)+(6x-12)\qquad\text{combine like terms}\\\\=(-3x+6x)+(9-12)\\\\=\boxed{3x-3}\\\\===========================[/tex]
[tex]4)\\\left(\dfrac{1}{4}x+10\right)+\left(\dfrac{1}{2}x-7\right)\qquad\text{combine like terms}\\\\=\left(\dfrac{1}{4}x+\dfrac{1}{2}x\right)+(10-7)\\\\=\left(\dfrac{1}{4}x+\dfrac{1\cdot2}{2\cdot2}x\right)+3\\\\=\left(\dfrac{1}{4}x+\dfrac{2}{4}x\right)+3\\\\=\boxed{\dfrac{3}{4}x+3}\\\\===========================[/tex]
[tex]5)\\(3x+5)-(2x+2)\\\\=3x+5-2x-2\qquad\text{combine like terms}\\\\=(3x+2x)+(5-2)\\\\=\boxed{5x+3}\\\\===========================[/tex]
[tex]6)\\10-8=\boxed{2}\\\\===========================[/tex]
[tex]7)\\7.8x-2.5x=\boxed{6.3x}\\\\===========================[/tex]
[tex]8)\\(5.8x+10)-(3.4x+8)\\\\=5.8x+10-3.4x-8\qquad\text{combine like terms}\\\\=(5.8x-3.4x)+(10-8)\\\\=\boxed{2.4x+2}\\\\===========================[/tex]
[tex]9)\\(8x-2)-(2x+8)\\\\=8x-2-2x-8\qquad\text{combine like terms}\\\\=(8x-2x)+(-2-8)\\\\=\boxed{6x-10}\\\\===========================[/tex]
[tex]10)\\(-4x-3)-(-4x-3)\\\\=-4x-3-(-4x)-(-3)\\\\=-4x-3+4x+3\qquad\text{combine like terms}\\\\=(-4x+4x)+(-3+3)\\\\=0+0\\\\=\boxed{0}\\\\\text{You could do it shorter.}\\\text{The result will be 0 because we subtract}\\\text{ the same expressions from each other.}[/tex]
