Answer:
 12<x≤12.2
Step-by-step explanation:
To fit in an existing frame, the length, x, of a piece of glass must be longer than 12 cm but not longer than 12.2 cm. 
The length of frame is x cm. 
Length of frame must be longer than 12 cm.
Inequality,  x>12 
 Length of frame not longer than 12.2 cm 
In equality, x≤12.2
Now we make compound inequality of question 
"Length of frame, x must be longer than 12 cm and not longer than 12.2 cm" 
Inequality: 12<x≤12.2
Length of glass fit in the frame, 12<x≤12.2
Hence, The inequality 12<x≤12.2