C) The +10 is because you already have 10 coins, that will not change. The 6x is because with each passing day, the number of coins increase by 6 (x represents days). The equation then turns into y=6x+10
4/3 is not a valid fraction for this type of problem so I am going to assume that it is 3/4. If this is a case she will need 1 and 1/4 more cups of sugar.
