Step 1: Write out the formula for finding the area of a rhombus
[tex]\begin{gathered} \text{Area }=\frac{AC\times DB}{2} \\ \text{ Where} \\ AC\text{ and DB are the diagonals of the rhombus } \end{gathered}[/tex]Step 2: Substitute the given values to find AC
[tex]\begin{gathered} \text{ Area }=45\text{ square units} \\ DB=6\text{units} \end{gathered}[/tex]Therefore,
[tex]\begin{gathered} \frac{6AC}{2}=45 \\ 3AC=45 \\ \text{ Dividing both by 3, we have} \\ \frac{3AC}{3}=\frac{45}{3} \\ AC=15 \end{gathered}[/tex]Hence, AC is 15 units