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

How many coins are tails up?

How many coins in all?

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

6 tails added

total=heads+tails

heads=16

tails=18+6=24

total=16+24

total=40

6 tails added

40 total coins