area of triangle = 8cm sq. ( i.e 1/2 ar of ||gm)
2*8= 4*b ( 2*ar of triangle = ar of ||gm or base* height)
if a triangle and a parallelogram are on the same base and between the same parallels, area of triangle= 1/2 area of ||gm.
therefore, base of the parallelogram is 4 cm. pls mark as 5 stars if this helped! I spent lot of time solving this 4 u.