If an angle is acute, then the measure of its complement must be greater than the measure of its supplement ? true or false

This is false.
Complement equals to 90° and Supplementary equals to 180°.
Since you given angle is acute its other angle must be small than 90.
Let's say your acute angle is 35°.
Your other angle would equal 55°.

On the other hand if it was Supplementary then:
Let still use the 35° example.
35°+55° would not be Supplementary. It would have to be larger like 125°.

Maybe fx = lxl because of the way the x is positioned is that what he