If the weight of the iron block is x grams and the weight of the copper block is y grams, there are: (1) 4x+10y = 38; (2)3x+5y=2 1

From (1): 4x = 38-10y, x = (38- 10y)/4, substituting (2): 3 [(38-10y)/4]+5y =

3(38- 10y)+20y=84

1 14-30y+20y=84

- 10y=-30

y=3

Because x=(38- 10y)/4.

x=(38-30)/4

x=2

Conclusion: An iron block weighs 2g and a copper block weighs 3g.