Find the grams of iron in 79.2 g of fe2o3.

First you find the RFM (Relative Formula Mass) of Fe2O3
Fe2 = 56 x 2
= 112
O3 = 16 x 3
= 48

112 + 48 = 160

Moles = mass/RFM
           = 79.2/160
           =0.495

Then you rearrange the formula
Mass= moles x RFM
        = 0.495 x 112
        = 55.44 g
(To find mass of Iron have to use RFM of total iron in the substance example Fe2 ^^)

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.