so first of all you need to know that in 1 quart there is 31.9995 ounces so since shes says there is 2 quarts lets do the math:)
31.9995 x 2 = 63.999 ounces
now she says she took 8 mugs and filled them up each with 6 and 3/4 ounces. lets do the math:)
6 and 3/4 x 8 = 30 ounces
now lets subtract that from our 2 quarts or 63.999 ounces
63.999 - 30 = 33.999
so we have 33.999 fluid ounces left in the jar:)
hope this helps lol
