factorise fully \( 6.3 a x+3 a y-x-y \)

To factorise the expression \( 6.3 ax + 3ay - x - y \), we can start by grouping the terms. First, we can rearrange and group the terms related to \(a\) and those without: \[ (6.3 ax + 3ay) + (-x - y) \] Next, we can factor out common terms from each group. From the first group, we can factor out \(3a\): \[ 3a(2.1x + y) - (x + y) \] Now, we see that both parts have a common factor of \((2.1x + y)\): \[ (3a - 1)(2.1x + y) \] Thus, the fully factorised form of the given expression is: \[ (3a - 1)(2.1x + y) \]