Question 570735
It is obvious that we have to find the length & width of the hole and the sheet.

the length of hole =x which is 1cm less than the length of the sheet
x=y-1

Area = L*W

width of hole =2cm
Length of hole = x cm

{{{highlight(Area of hole = 2x)}}}
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width of sheet = 7/2 cm

length of sheet = y

{{{highlight(area of sheet = (7y/2) cm^2)}}}

Area of sheet - area of hole = balance area =11cm^2



{{{(7y/2) - 2x = 11}}}

substitute x in this equation

{{{(7y/2)-2(y-1)=11)}}}

multiply the equation by 2 to eliminate the denominator
7y-4(y-1)=22
7y-4y+4=22
3y=18
/3
]y=6 cm 
length of sheet = 6 cm
length of hole is 1 less than length of sheet
so length of hole = 6-1 =5 cm


CHECK
area of sheet - area of hole = 11
7/2 * 6 - 5*2=11 

11=11