Answer:
90 g of water should be added and he will make 900 g of solution.
Step-by-step explanation:
Let x g be the amount of salt Ilya add to 810g of water to make 10% solution. Then 810+x g is the amount of new solution. Thus,
810+x - 100%,
x - 10%.
Mathematically,
[tex]\dfrac{810+x}{x}=\dfrac{100}{10},\\ \\10(810+x)=100x,\\ \\8100+10x=100x,\\ \\100x-10x=8100,\\ \\90x=8100,\\ \\x=\dfrac{8100}{90}=90\ g.[/tex]
So 90 g of water should be added and he will make 810+90=900 g of solution.
