Teresa needs 2/3 tablespoons of fertilizer for 5 gallons of water.
To find how many tablespoons of fertilizer Teresa needs for 5 gallons of water, we can set up a proportion using the given information. We know that she uses 2/3 tbsp of fertilizer for every 5/6 gal of water. Let x be the number of tablespoons needed for 5 gallons of water. The proportion is: 2/3 tbsp / 5/6 gal = x tbsp / 5 gal. Cross-multiplying, we get: (2/3) * (5 gal) = (5/6) * x tbsp. Simplifying, we find: 10/18 tbsp = 5x/6 tbsp. Cross-multiplying again, we have: (10/18) * 6 tbsp = 5x tbsp. Simplifying further, we get: 10/3 tbsp = 5x tbsp. Dividing both sides by 5, we find: x = (10/3) / 5 tbsp. Simplifying this expression, we have: x = 2/3 tbsp. Therefore, Teresa needs 2/3 tablespoons of fertilizer for 5 gallons of water.