Solve this 2 step equation 3x-7=20

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?

In a small section of a stadium there are 40 spectators watching a game between the cook islands and fiji. they all support at least one of the two teams. 25 spectators support the cook islands and 16 of these support both teams. how many support only fiji?

Peyton's field hockey team wins 4 games out of every 7 games played. her team lost 9 games. how many games did peyton's team play?