First convert the mixed number to the improper fraction:
[tex]2\dfrac{3}{4}=\dfrac{2\cdot4+3}{4}=\dfrac{11}{4}[/tex]
Make the product:
[tex]a=2\dfrac{3}{4};\ b=\dfrac{4}{5}\\\\ab=2\dfrac{3}{4}\cdot\dfrac{4}{5}=\dfrac{11}{4}\cdot\dfrac{4}{5}[/tex]
canceled 4
[tex]=\dfrac{11}{\not4_1}\cdot\dfrac{\not4^1}{5}=\dfrac{11}{1}\cdot\dfrac{1}{5}=\dfrac{11}{5}=\dfrac{10+1}{5}=2\dfrac{1}{5}[/tex]
