how do I solve y+8.1=9?

y + 8.1 = 9
y = 9 - 8.1
y = 0.9

y=9-8.1
y=0.9

y = 0.9

Because 0.9 + 8.1 = 9

y = 0.9

y + 8.1 = 9

Subtract 8.1 from both sides:

y = 0.9

1. y+8.1=9
2. Remove 8.1 so it's just y=answer
3. y+8.1=9
-8.1 -8.1
4.y=.9

here's how to think of it :
the aim is to keep "y" on one side,and a number on the other side , so what's there on the "y"'s side ? a ( +8.1) ,how do you get rid of that ? by adding (-8.1) to both sides of the equation so it stays balanced (because you added the same amount to both sides ,so we didn't miss with the equality ) .
hence :
y+ 8.1 + (-8.1) = 9 + (-8.1)
you can rewrite it as :
y + 8.1 - 8.1 = 9 - 8.1 ( because + - = - )
->> y = 9 - 8.1
y = 0.9

y=0.9

take 8.1 and - 9
so then y= 0.9