Mei Mei paid $11.70 for a book and 8 identical pens.Wen Liang paid $14.40 for the same book and 11 identical pens.Find the cost of 1 pen.

Step 1: Let's denote the cost of the book as B and the cost of one pen as P.

Step 2: From the problem, we know that Mei Mei paid $11.70 for a book and 8 pens. So, we can write this as an equation: B + 8P = 11.70

Step 3: We also know that Wen Liang paid $14.40 for the same book and 11 pens. We can write this as another equation: B + 11P = 14.40

Step 4: Now we have a system of two equations, and we can solve it. Let's subtract the first equation from the second one: (B + 11P) - (B + 8P) = 14.40 - 11.70. This simplifies to 3P = 2.70

Step 5: Finally, to find the cost of one pen, we divide both sides of the equation by 3: P = 2.70 / 3 = $0.90

So, the cost of one pen is $0.90.