How do you deal with 3 simultaneous equations? (Struggling with Q7 of AQA specimen paper 1)

If you need to solve them, then you just plug your way through the algebra to get to the answer.

In this question (Q7) you need to find the value of a constant such that there is no solution to the three equations:

1. Run through/check the student understands converting simultaneous equations into a matrix.
   
2. Go over the rules for how the determinant of the matrix relates to the number of solutions, e.g. for no solutions the determinant is zero.
   
3. Help the student get to the answer.