Final answer:
The equation that represents this situation is 20 + 0.15x = 24.75. To find the value of x, subtract 20 from both sides and divide by 0.15.
Step-by-step explanation:
The equation that represents this situation is:
20 + 0.15x = 24.75
Where x represents the number of minutes you read. In this equation, 20 is the flat fee donated by your granny and 0.15 is the donation per minute from your mom.
To solve the equation, you can subtract 20 from both sides and then divide by 0.15 to find the value of x.