Answer:
[tex]\$(990-t)[/tex]
Step-by-step explanation:
The correct question is
Susan works as a tutor for $10 and hour, and as a waitress for $11 an hour. This month, she worked a combined total of 90 hours at her two jobs. Let t be the number of hours Susan worked as a tutor this month. Write an expression for the combined total dollar amount she earned this month
Let
t -----> the number of hours that Susan work as a tutor
y ----> the number of hours that Susan work as a waitress
z ---> the combined total dollar amount she earned this month
we know that
[tex]t+y=90[/tex]
[tex]y=90-t[/tex]-----> equation A
we know that
The combined total dollar amount she earned this month is equal to the number of hours that Susan work as a tutor multiplied by $10 plus the number of hours that Susan work as a waitress multiplied by $11
[tex]z=10t+11y[/tex] ----> equation B
substitute equation A in equation B
[tex]z=10t+11(90-t)[/tex]
[tex]z=10t+990-11t[/tex]
[tex]z=990-t[/tex]
therefore
The expression for the combined total dollar amount is $(990-t)