To find out what grade Clariza needs on her final exam to achieve an average of 85, we can set up the following equation.
Let \( x \) be the grade she needs on her final exam.
The average is calculated as:
\[ \text{Average} = \frac{\text{Sum of all grades}}{\text{Total number of grades}} \]
In Clariza's case, she has already completed 4 assignments, and her final exam will be the 5th grade. The sum of her current grades is:
\[ 90 + 82 + 84 + 88 = 344 \]
Thus, the equation for achieving an average of 85 is:
\[ \frac{344 + x}{5} = 85 \]
Now, we can multiply both sides by 5 to eliminate the fraction:
\[ 344 + x = 425 \]
Next, we subtract 344 from both sides:
\[ x = 425 - 344 \]
\[ x = 81 \]
So, Clariza must score 81 on her final exam to achieve an overall average of 85.