Find a7 in the arithmetic sequence with a1=-28 and d=10

Which inequality has a dashed boundary line when graphed ?

Collin did the work to see if 10 is a solution to the equation r/4=2.4

The perimeter of an equilateral triangle is 4 cm more than the perimeter of a square and the length of a side of the triangle is 8 cm more than the length of a side of the aware. find the length of a side of the equilateral triangle