math problem solving
posted by nikki .
mr. mancho, my great dane, ate 125 hot dogs over a fiveday period. each day he ate seven more hot dogs than on the previous day. how many hot dogs did he eat on the first day

Let X be the number eaten the first day.
X + (X+7) + (X+14) + (X+21) + (X+28) = 125
5X + 70 = 125
5X = 55
X = 11
Check: 11 + 18 + 25 + 32 + 39 = 125
This couls have been obtained more easily (and without algebra) by recognizing that the number consumed on the third day (25) was the average for the fiveday period. 
eleven