(a) Using graphical method, solve the following system of equations: 3 x+y+4=0 and 3 x-y+2=0

Using graphical method, solve the following system of equations : \[3 x+y+4=0 \text { and } 3 x-y+2=0 \]

Tara scored $\displaystyle 40$ marks in a test, getting $\displaystyle 3$ marks for each right answer and losing $\displaystyle 1$ mark for each wrong answer. Had $\displaystyle 4$ marks been awarded for each correct answer and $\displaystyle 2$ marks been deducted for each wrong answer, then Tara would have scored $\displaystyle 50$ marks. Assuming that Tara attempted all questions, find the total number of questions in the test.