How many times does 0.5 go into 10.80?

Do not comment if you aren’t going to . create a real-life situation and create a system and show how it might be modeled algebraically with a system of equations (or inequalities) show all work include a few sentences explaining the situation, your variables of choice and what each represents, and how you would set it up and solve it algebraically. !

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

How to do this , and can some one explain