Which equation is equivalent to x2 + 2x – 3 = 0?​

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?

Apatient is to be given 35 milligrams of demerol every 4 hours. you have demerol 50 milligrams/milliliter in stock. how many milliliters should be given per dose?

How many kilograms of a 5% salt solution and how many kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution?