Mohon bantuannya, saya kurang dalam matematika.

a.6/8x2 2/4x3/9=6/8x10/4x3/9=60/32x3/9=180/278=90/139
b.2 2/5x1 2/8x6/7=12/5x10/8x6/7=120/40x6/7=720/280=18/40=9/20
c.2 4/6x4/8x2 2/5=16/6x4/8x12/5=64/48x12/5=768/240=64/20=32/10=16/5
d.3 3/5x2 3/6x3/4=18/5x15/6x3/4=810/300=162/60=81/30