3=a+b

Solution for 3=a+b equation:

Simplifying
3 = a + b

Solving
3 = a + b

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 + b

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

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

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

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

Simplifying
a = 3 + -1b