Can you use addition or subtraction to solve any system

What is the slope of a line that is perpendicular to y = 3x + 1

Which linear equations have an infinite number of solutions? check all that apply.  (x  –  3/7)  =  2/7(3/2x  –  9/14)8(x  +  2)  =  5x  –  1412.3x  –  18  =  3(–6  +  4.1x)(6x  +  10)  =  7(x  –  2)4.2x  –  3.5  =  2.1 (5x  +  8)

1.based of the diagrams what is the the value of x? 2.how would you verify your answer for x