How do I solve this?

Question

Great Ore mining Company claims that it cost $20 to mine 1g of gold ore, and $10 to mine 1g of silver ore. They also state that mining gold and silver ore on a particular day cost the company $1,600.00. The total amount of ore minded that day was 100g. How much gold ore was minded and how much silver ore was minded?

Answer 1

Let x = the number of grams of gold ore mined

Let y = the number of grams of silver ore mined

x + y = 100       y = 100 - x

20x + 10y = 1600

20x + 10(100 - x) = 1600

20x + 1000 - 10x = 1600

10x = 600

x = 60 gm

y = 100 - x = 100 - 60

y = 40 gm