Answer: 16/24
Step-by-step explanation: You should convert 7/8 and 2/3 to get a common denominator, in this situation the common denominator is 24. You multiply 2/3 by 8 on both sides of the fraction and the same with 7/8 except with 3. When you convert it 7/8 becomes 21/24 which is the total amount of grapes she bought, the amount she used comes out to be 16/24.