Answer:
86%
Explanation:
We have been given that Mildred has seven grades on her report card. The overall average of these grades is 77%.
Since her average grades are 77, so total scores on 7 grades would be
![77* 7=539](https://img.qammunity.org/2020/formulas/mathematics/middle-school/fn6qjbg0e0mutubthjw8sz90ly4sa67t38.png)
As her grades on English were incorrectly recorded as 18% instead of 81%, so we will find the difference of grades.
![81-18=63](https://img.qammunity.org/2020/formulas/mathematics/middle-school/r2xf4p2fjxhbdtdbxl1tptiepgyb0y8cg6.png)
Since the incorrect total is 63 less than actual total, so we will add 63 points to total grades as:
![\text{Actual sum}=539+63=602](https://img.qammunity.org/2020/formulas/mathematics/middle-school/uw2awc0n30sj4i6d651lefce8baeio7rrc.png)
Now we will divide actual sum by 7 to find actual report card average.
![\text{Actual report card average}=(602)/(7)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6lsh0owm1h2es3rzhukybw6az4knwqsuv5.png)
![\text{Actual report card average}=86](https://img.qammunity.org/2020/formulas/mathematics/middle-school/1pcdh0kji1xc434rq5ft8e6dyec3s278c1.png)
Therefore, Mildred's actual report card average is 86%.