17=[a]-3

Solution for 17=[a]-3 equation:

Simplifying
17 = [a] + -3
17 = a + -3

Reorder the terms:
17 = -3 + a

Solving
17 = -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.
17 + -1a = -3 + a + -1a

Combine like terms: a + -1a = 0
17 + -1a = -3 + 0
17 + -1a = -3

Add '-17' to each side of the equation.
17 + -17 + -1a = -3 + -17

Combine like terms: 17 + -17 = 0
0 + -1a = -3 + -17
-1a = -3 + -17

Combine like terms: -3 + -17 = -20
-1a = -20

Divide each side by '-1'.
a = 20

Simplifying
a = 20