Question

marianne buys 16 bags of potting soil that comes in 5/8 lb. bags. how many pounds of potting soil foes she has.

Answer 1

One bag of soil is 5/8 pounds.
you have 16 of them.
just multiply 16 by 5/8.
you could just type it into your calculator, or you could do it the long way:
$16 * \frac{5}{8} \\ \frac{16*5}{8} \\ \frac{8*2*5}{8} \\ 2*5\\10$

she has 10 pounds of potting soil.