Final answer:
The expressions that represent a total gain of $70 are 100 + (-30), 20 + (50), and 70.
Step-by-step explanation:
To find expressions that represent a total gain of $70, we need to add numbers with a positive sign. The expressions that apply are:
- 100 + (-30): This expression equals 70.
- 20 + (50): This expression also equals 70.
- 70: This expression itself is equal to 70.
So, the expressions that represent a total gain of $70 are 100 + (-30), 20 + (50), and 70.