let first parallel side by x
then the second parallel side = x + 4 (not 4x)
area of trapezium = 1/2 ×(sum of parallel sides)× height
or 475 = 1/2 × (x + x + 4) ×19
or 475×2/19 = (2x+4)
or 50 = 2x + 4
or 2x = 50 - 4
or x = 46/2
or x = 23
so, first parallel side = 23 cm
second parallel side = 23 + 4 = 27 cm