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(x) atoms of 35Cl weigh ? (y) atoms of 37Cl weigh ?
Then 35x + 37y = 3550
Using these two equations to solve for (x) and (y):
35x + 37y = 3550 35x + 37y = 3550
(x + y = 100) x 35 35x + 35y = 3500
Changing signs for the second equation (as in simultaneous equations):