1+2=a

Solution for 1+2=a equation:

Simplifying
1 + 2 = a

Combine like terms: 1 + 2 = 3
3 = a

Solving
3 = a

Solving for variable 'a'.

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

Add '-1a' to each side of the equation.
3 + -1a = a + -1a

Combine like terms: a + -1a = 0
3 + -1a = 0

Add '-3' to each side of the equation.
3 + -3 + -1a = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -1a = 0 + -3
-1a = 0 + -3

Combine like terms: 0 + -3 = -3
-1a = -3

Divide each side by '-1'.
a = 3

Simplifying
a = 3