You have 16 coins that are heads up and 18 coins that are tails up. After you add some coins that are tails up, the ratio of heads up to tails up is 1 to 1.5
so 16=heads 18=tails after you add some tails 18+x
ratio of heads to tails is 1:1.5 heads=16, didn't change tails=18+x
so 1:1.5=16:18+x fractionify 1/1.5=16/(18+x) 1/1.5=2/3 2/3=16/(18+x) mutiply both sides by (3)(18+x) 2(18+x)=3(16) 36+2x=48 subtract 36 from both sides 2x=12 divide 2 x=6
