You need to find a scale factor of dilation (probably contraction) to make the replica.
Given that the units of the original painting are centimeters and the units of the sheet of paper are in inches, you have to convert one of the units.
I choose to covert inches to centimeters.
To do that, use the conversion factor 1 = 2.54 cm / inch
=> 8.5 in * [2.54 cm/in] = 21.59 cm
=> 11 in * [2.54 cm/in] = 27.94 cm
Now determine the scale factor to convert 77 cm to 27.94 cm and 53 cm to 21.59 cm. That just require use of division operation:
77 / 27.94 = 2.76
53 / 21.59 = 2.45
Then the higher scale factor is the relevant one, and you have to reduce the original painting by a factor of (1 / 2.76) which will lead to fit in the sheet of paper.
