In part 1, we are given with two equations and according to the degrees of freedom rule, two equations should solve two unknowns. The number of solutions is a pair of two variables. Hence the answer is B In part 2, this is just a matter of substitution or in a long way solve each expressions for their x and y. The answer should be D. In part 3, we can use a calculator to solve the system of equations. Using addition to eliminate y, too, the answer is C.
