Step 1
Find out the total number of flowers Paula and Ava had
[tex]\text{They had together 15 + 13= 28 flowers}[/tex]
Step 2
Find how many pages they filled
[tex]\begin{gathered} Since\text{ they have 28 flowers, and eight flowers are on each page, we have} \\ \frac{28}{8}=\text{ 3 complete set of 8 flowers remainder 4 flowers} \end{gathered}[/tex]
Hence 3 pages will be filled and they will have 4 flowers left.
Step 3
Find how many flowers they need to fill the last page.
[tex]\begin{gathered} T\text{hey put 8 flowers in each page of the scrapbook.} \\ \text{They have 4 flowers left, so they will n}eed\text{ 4 more flowers to get the 8 required for a page} \end{gathered}[/tex]
Hence, they will need 4 more flowers to fill the last page