Solving Simultaneous Equations by Elimination

This worksheet is designed to solve equations by elimination.
I wrote this worksheet to give positive values of x and y only for the 12 questions in the main section (as I couldn't find one online at the time) because I wanted to check their skill at solving them and not their skill at calculating with directed numbers. I wrote the challenge section to provide some differentiation in the lesson as each of these gives 1 positive and one negative solution - the last one involves decimals too.