How to find the average atomic mass of an element

A new element, schoolium, (SI), found only in schools occurs in the following proportions: 9.750% SI-750 and 90.250% SI-752. Find average atomic mass in significant figures.

I'm a little confused. Especially, what do the 750 and 752 mean?

The 750 and 752 are the atomic masses. That is to say that a 'lump' of this element contains 9.75 % atoms which weigh 750 u and 90.25 which weigh 752 u.

Firstly find 1% of each of the atomic mass, then multiply by the percentage, finally add the two numbers

750 / 100 = 7.5 * 9.75 = 73.125
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752 / 100 = 7.52 * 90.25 = 678.68

= 751.805 u

EDIT:The plus sign isn't showing :/