Solve -8x +y=23 and -x+6y=-3 using substitution method

Daniel expanded the expression as shown below -2(-8x-4y+3/4)=-10x-8y-11/4 what errors did he make? check all that apply

Atheater wants to build movable steps that they can use to go on and off the stage. they want the steps to have enough space inside so they can also be used to store props. how much space is inside the steps?

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.