Simplify.

a) [[$ \displaystyle\frac {4 \cdot 5x} {4} = $]]

b) [[$ \displaystyle\frac {2 \cdot 3a} {3a} = $]]

c) [[$ \displaystyle\frac {2x \cdot 6x} {3x} = $]]

d) [[$ \displaystyle\frac {-5 \cdot 3x} {10x} = $]]

Take a picture of your solution and return it to the submission folder.