To make a 30% sugar syrup using 75 g of sugar, you need to add an amount of water that will bring the total solution mass to 250 g (100% / 30% = 100 / 0.3 = 250 g). The mass of sugar in the solution will then be 30% of the total mass.
The amount of water required can be calculated as follows:
Water = Total mass - Mass of sugar
Water = 250 g - 75 g
Water = 175 g
So, you would need to add 175 g of water to the 75 g of sugar to make a 30% sugar syrup. The final solution would have a total mass of 250 g and contain 225 g of sugar (75 g + 175 g).