99-100=y

Solution for 99-100=y equation:

Simplifying
99 + -100 = y

Combine like terms: 99 + -100 = -1
-1 = y

Solving
-1 = y

Solving for variable 'y'.

Move all terms containing y to the left, all other terms to the right.

Add '-1y' to each side of the equation.
-1 + -1y = y + -1y

Combine like terms: y + -1y = 0
-1 + -1y = 0

Add '1' to each side of the equation.
-1 + 1 + -1y = 0 + 1

Combine like terms: -1 + 1 = 0
0 + -1y = 0 + 1
-1y = 0 + 1

Combine like terms: 0 + 1 = 1
-1y = 1

Divide each side by '-1'.
y = -1

Simplifying
y = -1