The scoring in a certain game is based on the number of red tokens and blue tokens a player has. One player has red and blue tokens in a ratio of 7:10. Then she wins 10 more red tokens, changing her ratio of red to blue tokens to 4:5. How many total tokens does she have after winning the 10 red tokens?
that takes too long. You just guess by 70 :100 and then just add the ten and see that it gives you 80:100 = 8:10 = 4:5 — add the 80 and the 100 get 180