If you plug in 4 for x, then divide each side, the two sides will be equal. The right side top and bottom numbers are proportionate to those on the left because 14 * 4= 56 and 4 * 4= 16. The right side is just a multiple of 4 of the left side. 4 goes into 14 three and a half times, so 16 will go into 56 three and a half times too.
14/4 = 56/16
3.5= 3.5
Hope this helps! :)