Will you help me solve please

Which function has the same domain as y=2x

How many solutions does the nonlinear system of equations graphed bellow have?

Four individuals pool money together to start a new business and agree to split the profits equally. n invests $6,000, x invests $2,000, y invests $8,000 and z invests $4,000. if the profits for the first month were $100,000, y receives than if the profits were divided in proportion to how much they invested.