Answer: Only 1 ounce of ham was left.
Step-by-step explanation: Given that Lauren bought 20 ounces of sliced ham, out of which she used three-fourth of the ham to make sandwiches for her friends and one fifth of the ham in an omelette.
We are to find the ounces of ham that were left.
Ounces of ham used to make Sandwiches is given by
[tex]H_s=\dfrac{3}{4}\times 20=3\times 5=15~\textup{ounces},[/tex]
and ounces of ham that were used in an omelette is given by
[tex]H_o=\dfrac{1}{5}\times 20=4~\textup{ounces}.[/tex]
So, total ounces of ham that were used = 15 + 4 = 19 ounces.
Therefore, ounces of ham that left = 20 - 19 = 1 ounce.
Thus, only 1 ounce of ham was left.