Final answer:
The expression 18x - 42y + 30z factorises to 6(3x - 7y + 5z), where 6 is the common factor.
Step-by-step explanation:
The question asks to factorise the expression 18x - 42y + 30z. Factorising is an essential skill in algebra which involves breaking down an expression into its simplest parts or factors. In this case, we look for a common factor among all three terms.
A common factor for 18, 42, and 30 is the number 6. Taking 6 out as a common factor, we rewrite the expression as 6(3x - 7y + 5z). This is the factorised form of the expression, and it cannot be simplified further as the terms inside the parenthesis do not have any further common factors.