To model the situation with an equation, you can represent the amount Nandita earned by babysitting as \( x \).
According to the information given, Nandita earned a total of 224 dollars last month. She earned 28 dollars by selling cards, and the rest of the money came from babysitting.
You can express this situation with the following equation:
\[ x + 28 = 224 \]
Here, \( x \) represents the amount Nandita earned from babysitting. To find \( x \), you can solve the equation:
\[ x = 224 - 28 \]
Calculating this gives:
\[ x = 196 \]
Thus, Nandita earned 196 dollars by babysitting last month.