I need help with is proof if -4(x-3) +5x=24,then x=12

Acircle has a diameter will endpoints of (-2,8) and (6, 4). what is the center of the circle

Players on the school soccer team are selling candles to raise money for an upcoming trip. each player has 24 candles to sell. if a player sells 4 candles a profit of$30 is made. if he sells 12 candles a profit of $70 is made

Is the power produced directly proportional to the wind speed, give reasons for your answer?