[Sleek]

suppose a nameless element (X) was found to occur in three different substances (A, B and C). The relative molecular masses of A, B, and C were found to be 27.40, 52.90 and 62.60 respectively, compared to an assigned value of exactly 2.00 for H2. Subsequently, these substances were subjected to elemental analysis and were found to contain 78.1%, 81.1% and 85.6% of X respectively by mass.

What is the (likely) relative atomic mass of X, on this scale?

what i did:
27.40 * 0.781 = 21.4
52.9 * 0.811 = 42.9
62.6 * 0.856 = 53.59

there is a hint that says

Work out the mass of X in the each of the molecules A, B, and C from the percentages of X and the molecular masses. Then find the highest common factor (also called the highest common divisor or the greatest common factor).

i have no idea how to get the common factor with those numbers..

[Borek]

Check if all these numbers are not multiplies of the smallest, or of the smallest difference between them.