Question

How many solutions exist for the following system of equations: 4x + y = 7 and 3x - y = 0 a. no solution b. one solution c. infinitely many d. cannot be determined

Answer 1

$4x+y=7 \\ \underline{3x-y=0} \\ 4x+3x=7+0 \\ 7x=7 \ \ \ |\div 7 \\ x=1 \\ \\ 3x-y=0 \\ 3 \times 1-y=0 \\ 3-y=0 \ \ \ |+y \\ y=3 \\ \\ (x,y)=(1,3)$

The answer is B. one solution.