Negative twelve less than or equal to three times a number minus six less than six solve

Ineed if you could explain and give me the answer you! this needs done

Phyllis and chen are saving money to go to a football game. each friend starts with some money and saves a specific amount each week. phyllis made a graph to show the total she has saved at the end of each week. chen wrote an equation to show the total, y, he has saved at the end of each week, x. y = 15x + 15 compare the amount that each friend has when both friends start saving. select the correct answer from the drop-down menu to complete the statement. phyllis starts with $ and chen starts with $

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?