Simplifying
-1(2.1c + -4d) = 0
(2.1c * -1 + -4d * -1) = 0
(-2.1c + 4d) = 0
Solving
-2.1c + 4d = 0
Solving for variable 'c'.
Move all terms containing c to the left, all other terms to the right.
Add '-4d' to each side of the equation.
-2.1c + 4d + -4d = 0 + -4d
Combine like terms: 4d + -4d = 0
-2.1c + 0 = 0 + -4d
-2.1c = 0 + -4d
Remove the zero:
-2.1c = -4d
Divide each side by '-2.1'.
c = 1.904761905d
Simplifying
c = 1.904761905d <-- this is the answer
