Step-by-step explanation:
Let w be the work of waxing.
Rosita can wax her car in 2 hours or 120 minutes.
Time taken by Rosita = 120 minutes
[tex]\texttt{Rate of Rosita = }\frac{W}{120}[/tex]
Let time taken by Helga be t,
[tex]\texttt{Rate of Helga = }\frac{W}{t}[/tex]
When she works together with Helga, they can wax the car in 45 minutes.
We have
[tex]\frac{W}{\frac{W}{120}+\frac{W}{t}}=45\\\\120t=45(120+t)\\\\120t=5400+45t\\\\t=72minutes[/tex]
Time taken by Helga to wax the car is 72 minutes
