d-a=a+c

Solution for d-a=a+c equation:

Simplifying
d + -1a = a + c

Reorder the terms:
-1a + d = a + c

Solving
-1a + d = a + c

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.
-1a + -1a + d = a + -1a + c

Combine like terms: -1a + -1a = -2a
-2a + d = a + -1a + c

Combine like terms: a + -1a = 0
-2a + d = 0 + c
-2a + d = c

Add '-1d' to each side of the equation.
-2a + d + -1d = c + -1d

Combine like terms: d + -1d = 0
-2a + 0 = c + -1d
-2a = c + -1d

Divide each side by '-2'.
a = -0.5c + 0.5d

Simplifying
a = -0.5c + 0.5d