Given the average score is 90 on four tests. The scores on first three tests were 94, 78, and 92. Let the lowest score she can make on the last test be x. Then it follows that
[tex]\begin{gathered} \frac{94+78+92+x}{4}=90 \\ \frac{264+x}{4}=90 \end{gathered}[/tex]
Cross multiply
[tex]\begin{gathered} 264+x=4\times90 \\ 264+x=360 \\ x=360-264 \\ x=96 \end{gathered}[/tex]
Hence, the lowest score she can make on the last test and still get an A is 96
