[tex]a)\ 16\cdot\frac{5}{8}=\\\\\frac{80}{8}=10\\\\Marianne\ buys\ 10\ pounds\ of\ potting\ soil.\\\\b)\ She\ has\ 10\ pounds,\ so\ she\ need\ bags\ only\ for\ 3\ punds.\\\\3:\frac{5}{8}=\\\\3\cdot\frac{8}{5}=\frac{24}{5}=4.8\\\\She\ need\ 5\ additional\ bags.[/tex]