Hi i just like kinda forgot what that line above the two numbers in 2.21 mean. Can you help me?

Compare these two waves: the blue and orange waves have the same pitch, but the blue wave is louder. the blue and orange waves have the same volume, but the blue wave has a higher pitch. the orange wave has a higher pitch, but the blue wave is louder. the blue wave has a higher pitch, but the orange wave is louder.

Write 17/20 as a decimal and as a percent.

What is the value of x in the following equation? -3x-2=2x+8