Any point on a country's production possibilities frontier represents a combination of two goods that an economy:

Any point on a country's production possibilities frontier represents a combination of two goods that an economy can produce. A production possibility frontier also know as PPF shows the maximum output that two goods or services can achieve when all of the resources are being used. For this graph to show the true possibilities, all of the resources have to be used to their full potential as efficiently as possible.

u = 30

continuing your method

= +

subtract from both sides

= - thus

= -

= ⇒ u = 30