Explanation
We are asked to find the score James needs to have on his 4th test to have an average of 85
Let his fourth score be x
Next, we will use the formula
[tex]Average=\frac{sum\text{ of scores}}{number\text{ of tests}}[/tex]
In our case, the total number of tests is 4
The sum of scores is
[tex]73+80+88+x[/tex]
The average is 85
So, solving for x
[tex]\begin{gathered} 85=\frac{73+80+88+x}{4} \\ \\ 85=\frac{241+x}{4} \end{gathered}[/tex]
Solving for x
[tex]\begin{gathered} 241+x=85\times4 \\ 241+x=340 \\ x=340-241 \\ x=99 \end{gathered}[/tex]
Therefore, James has to score 99 in his fourth test to have an average of 85
