for this problem, you can either use elimination or substitution. im going to use substitution.
solving it by substitution, you would have the equation -x + 4 = 2/3x - 1. from here you solve the equation for x, which equals 3.
then, by plugging in 3 to the bottom equation (easier to do because there arent any fractions), youd be able to find y, which equals 1.
keep in mind you can use the above method (substitution) or elimination to solve systems of equations.