Final answer:
Reese read 26 pages on Sunday, which can be determined by setting up the equation s + 2s = 78 and solving for s. Therefore, the correct answer is option 1.
Step-by-step explanation:
To determine how many pages Reese read on Sunday, we can set up an equation. Let's denote the number of pages Reese read on Sunday as s. Since Reese read twice as many pages on Saturday, she read 2s pages on that day.
The total number of pages read over the weekend is the sum of the pages read on both days, which gives us the equation s + 2s = 78. By combining like terms, we get 3s = 78. Reese read 26 pages on Sunday. To find the value of s, we divide both sides of the equation by 3, yielding s = 26. Therefore, Reese read 26 pages on Sunday.