x=16cm
y=17cm
Explanation:
area of the sheet = 4y
area of the hole = 3x
4y-3x=20
y=x+1, so let's substitute and solve for x
4(x+1)-3x=20
4x+4-3x=20
x+4=20
x=20-4
x=16
y=17
note: my keyboard is starting to act weird and I left out the units (cm) in the explanation to simplify things