18-4f=2d, if we know that 2d=8f that would mean 18 must equal 12f for this to be true. So, that’d mean 18 is 3 times bigger than 4f, if that is the case 4f must equal 6 since 6*3=18. Knowing this we divide 6 by 4 which equals 1.5. So f=1.5, we can rewrite this as 18-6=2d and then solve.
