Answer: 600 grams.
Explanation:
Let x be the amount of sugar syrup made by 15% sugar syrup using 90g sugar.
Also, 15% =0.15
Thus 15% sugar syrup =15% of x = 0.15x
According to the question, we have

Hence, 600 grams sugar syrup is made by 15% sugar syrup of 90g sugar.