Heeelp , please the 1st question on top

Lisa has three classes that each last 50 minutes. what is the total number of minutes of the three classes

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

Margie is practicing for an upcoming tennis tournament. her first serve is good 20 out of 30 times on average. margie wants to know the estimated probability that her first serve will be good at least four of the next six times she serves. how could she design a simulation for this scenario?