Final answer:
To find the number of pages in the book, we can set up a proportion using the information given. Since Joe has read 70% of the book, we can say that the number of pages he has read is 70% of the total number of pages in the book. By solving the proportion, we find that there are 30 pages in the book.
Step-by-step explanation:
To find the number of pages in the book, we can set up a proportion using the information given. Since Joe has read 70% of the book, we can say that the number of pages he has read is 70% of the total number of pages in the book. Let's represent the number of pages Joe has read as x, and the total number of pages in the book as y. The proportion can be set up as: 70/100 = x/y. To find the value of y, we can cross multiply and solve for y. Cross multiplying gives us 100x = 70y. Dividing both sides by 70 gives us x = (7/10)y. Since Joe has 3 pages left to read, we can substitute x = (7/10)y and solve for y: (7/10)y = (7/10)(3). This simplifies to y = 30. Therefore, there are 30 pages in the book.