Answer:
7 pieces
Explanation:
step 1
we know that
To find out how many more pieces of string are needed, divide the total length of the piece of string by 3/8 and the result subtract from 20 pieces
![4(7)/(8) : (3)/(8)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ig1jchht4xrvhpfair67elfs4nywe58dj5.png)
step 2
Convert mixed number to an improper fraction
![4(7)/(8)\ in=4+(7)/(8)=(4*8+7)/(8)=(39)/(8)\ in](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ua4eghes9iyzryduevvwh0gl6y03bppxft.png)
step 3
![(39)/(8) : (3)/(8)=13\ pieces](https://img.qammunity.org/2020/formulas/mathematics/middle-school/9kzs81khk47ecxm75fxhci7vlta9e2errt.png)
step 4
![20-13=7\ pieces](https://img.qammunity.org/2020/formulas/mathematics/middle-school/8yi6btlrzbgtmh7ikdccjckbo2vc9u8jy3.png)