Hint: There are several ways to proceed in this kind of problems, but usually the simplest and the one that will yield the most success on average is substituting.
Look at y variable and the expressions to which it is equal; substitute the easier-looking one in the more complicated. Applying this, we get: 2x+2=x^2+3x-4 x^2+x-6=0.
Solving this equation of 2nd degree, we have a=1, b=1, c=-6 and we get Δ=25 and the solutions are -3 and 2. Hence, we get that the only possible values for x are -3 and 2. To get the solutions, we have to also find the corresponding y-values: For x=-3, y=2x+2=-4. For x=2, y=6.
Hence, the 2 pairs of solutions are: (-3,-4) and (2,6)
All the ones with saving account number are not functions because the
outcome does not depend on the account number. It depends on
the amount in the account and the interest.