"Percent" or "%" means "out of 100" or "per 100", Therefore 15% can be written as #15/100#.
So we can write and solve this equation:
#15/100 = 1868/p#
#(color(red)(100)color(green)(p))/color(blue)(15) * 15/100 = (color(red)(100)color(green)(p))/color(blue)(15) * 1868/p#
#(cancel(color(red)(100))color(green)(p))/cancel(color(blue)(15)) * color(blue)(cancel(color(black)(15)))/color(red)(cancel(color(black)(100))) = (color(red)(100)cancel(color(green)(p)))/color(blue)(15) * 1868/color(green)(cancel(color(black)(p)))#
#p = 186800/15#
#p = 12453.bar3#
1,868 is 15% of #color(red)(12,453.bar3#