7/15×3/8+1/15×7/16+1/15×3又1/2
= 7/15×3/8+7/15×1/16+1/15×7/2
= 7/15×3/8+7/15×1/16+7/15×1/2
=7/15×(3/8+1/16+1/2)
=7/15×15/16
=7/16