Can anyone give some help on how I should go about creating a formula for this problem? Bob creates a new shade of paint by mixing black, red and white paint. He uses x litres of black paint. He uses 5 times as many litres of red paint than he uses of black paint. He uses 12 more litres of white paint than he uses of red paint. Altogether he produced 672 litres of the new shade of paint. Form an equation in terms of x and solve it to find the number of litres of each of the three different colours of paint used. Do I use different letters for the red and white paint or is it ok to call them 5x and 5(x + 12 ) ?