[tex]To \ find\ this\ rate\ you\ should\ divide\ her\ total\ salary\ by\\\\ total \ amount\ of\ working\ hours\\\\
total \ salary= 54\$\\\\
total\ amount\ of\ hours=2,5h+4,25h=6,75h\\\\
rate=\frac{54\$}{6,75h}=8\$\ per\ hour\\\\
She \ earns \ 8 \$ \ per\ hour. [/tex]