A gardener mixes compost (y y\,y kg) and topsoil (x x\,x kg) in the ratio 7:2 to make a potting mix.
Use this information to draw a graph showing the relationship between the mass of compost and the mass of topsoil.

The gardener uses 21 kg of compost. Use your graph to work out how many kg of topsoil should be used.
Practise Edexcel GCSE Maths Writing a Ratio as a Fraction or Linear Function with exam-style questions for Foundation and Higher tier. 60 questions, matched to the Edexcel GCSE Maths (1MA1) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.