Given:
A student's grades on three tests are 85,94 and 84.
The student must have an average of 90 or greater.
Let the score of the next test = x
So, the average will be:
[tex]\frac{x+85+94+84}{4}\ge90[/tex]Solve for x, Multiply both sides by 4
[tex]\begin{gathered} x+85+94+84\ge90\cdot4 \\ x+263\ge360 \\ x\ge360-263 \\ x\ge97 \end{gathered}[/tex]So, the answer will be:
The student must get 97 or greater to get an average A.