Big dig diamond company pulverizes 152 tons of rock for every 2 ounces of diamonds it finds. how many tons of rock must it grind up in order to locate 20 ounces of diamonds?

For this case what we can do is the following rule of three:
 152 > 2
 x > 20
 We clear the value of x:
 x = (20/2) * (152)
 x = 1520 tons
  
 in order to locate 20 ounces of diamonds the company needs: 
 x = 1520 tons of rock

Set square i think so