The intersection of two planes will be a line and the intersection of three planes will be a point. For this reason, in part A your answer will come out as the equation of a line, and for part B you just need to solve the three equations for x, y, and z.
Solve equation 1 for x:
Insert modified equation 1 into equation 2 for x:
Solve for z:
The Answer for A is: z=0.5y+1
4x+y-z=? —> What is this equation equal to?