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Hi,

width of a flat screen monitor is 4 times it's height
Let x and 4x represent the height and width respectively
Question states***
2*4x + 2*x = 120cm
10x = 120cm
x = 12cm, the height. The width is 48cm
CHECKING our Answer***
2*12cm + 2*48cm = 24cm + 96cm = 120cm