Solution:
The number of hours worked for the month is
[tex]=105[/tex]The amount earned as a tutor for one hour is
[tex]=7[/tex]The amount earned as a waitress for one hour is
[tex]=13[/tex]The number of hours Rachel worked as a tutor is
[tex]=t[/tex]Let the number of hours she worked as a waitress be
[tex]=x[/tex]The equation representing the total hours worked for the month will be
[tex]\begin{gathered} x+t=105 \\ x=105-t\ldots\ldots\text{.}(1) \end{gathered}[/tex]The amount of money Rachel earned as a tutor this month will be calculated as
[tex]\begin{gathered} =7\times t \\ =7t \end{gathered}[/tex]The amount of money Rachel earned as a waitress this month will be calculated as
[tex]\begin{gathered} =13\times x \\ =13x \end{gathered}[/tex]The expression to represent the combined total earned this month will be
[tex]=7t+13x\ldots\ldots\text{.}(2)[/tex]Substitute equation (1) in equation (2) above, we will have
[tex]\begin{gathered} x=105-t\ldots\ldots\text{.}(1) \\ =7t+13x\ldots\ldots\text{.(}2) \\ =7t+13(105-t) \\ =7t+1365-13t \\ =1365-6t \end{gathered}[/tex]Hence,
The expression for the combined total she earned this month = 1365 -6t