How to tell if a system of equations has no solution or infinitely many?

Acylinder and its dimensions are shown. which equation can be used to find v, the volume of the cylinder in cubic centimeters?

Asquare and an equilateral triangle have the same perimeter. each side the triangle is 4 inches longer than each side of the square. what is the perimeter of the square

What is the equation of the line that is parallel to the line with the equation y= -3/4x +1 and passes through the point (12,-12)