Assuming that there is 100g sugar water after the first addition, then there is 3g sugar, and the sugar accounts for 2% of the sugar water after the second addition, then this is * * * with 150g sugar water, 150- 100g = 50g, that is to say, 50g is added each time and 50g is added next time.

or

If the unit after adding water for the first time is 1, there will be 3% sugar and 2% sugar for the second time.

Then add 3%/2% water-1 = 0.5, then the third total * * is 1+0.5+0.5=2.

So the concentration is 3%/2= 1.5%.

or

Assuming that the total mass of sugar water is 100g and the concentration is 3% after adding water for the first time, the sugar is 3g and the water is 97g.

After adding x grams of water for the second time, the concentration became 3÷( 100+X)=2%, and the solution was x = 50g.

At this time, the total mass of sugar water is 150g.

After adding 50g of water for the third time, the concentration became 3÷( 150+50)= 1.5%.

I said three, do you understand?