The price of one necklace is $10 plus $2.75 per hour.
If the first necklace took one hour to be made, its price is:
[tex]\text{price}1=10+1\cdot2.75=10+2.75=12.75[/tex]If the second necklace took three hours to make, its price is:
[tex]\text{price}2=10+3\cdot2.75=10+8.25=18.25[/tex]Now, calculating the total price, we have:
[tex]\begin{gathered} \text{Total}=\text{price}1+\text{price}2=12.75+18.25 \\ \text{Total}=31 \end{gathered}[/tex]So the total price of both necklaces together is $31.00