Just asking for some tips for answering questions, such as:

1)Find a such that i-4k is perpendicular to the vector -3i + ak

2)Suppose x and y are vectors which are linearly independent and the following vector equation holds for some scalars a and b: 9x + a(x+y) = b(x-2y). Find a and b.

3)Suppose x and y are vectors which are linearly independent and the following vector equation holds for some scalars a and b: -4x + a(x+y) = b(x-3y). Find a and b.

Thanks for any help