Since the original question is not clear and contains various formatting errors, I'll rewrite it to make sense and follow the required formatting.

Given:
[tex]\[ +21.80 - 20c + 29.80 - 20c + 12 = - \square + 20c \][/tex]

Solve the equation.

Fill in the blank:
[tex]\[ - \square \][/tex]



Answer :

Alright, let's go through the steps to solve this expression:

Given the expression:
[tex]\[ +21.80 - 20c + 29.80 - 20c + 12 \][/tex]

Our goal is to simplify this expression and then match it with the form:
[tex]\[ -\square + 20c \][/tex]

1. Combine like terms on the left side:

- First, let's collect all the constants:
[tex]\[ 21.80 + 29.80 + 12 \][/tex]

- Then combine the constants:
[tex]\[ 21.80 + 29.80 = 51.60 \][/tex]
[tex]\[ 51.60 + 12 = 63.60 \][/tex]

- Next, we combine the [tex]\(-20c\)[/tex] terms:
[tex]\[ -20c - 20c = -40c \][/tex]

- Putting it all together, we combine the constants with the variable term:
[tex]\[ 63.60 - 40c \][/tex]

2. Rewrite the expression to isolate the square term:

- The simplified form is:
[tex]\[ 63.60 - 40c \][/tex]

- We need to match this with:
[tex]\[ -\square + 20c \][/tex]

- To do that, we equate:
[tex]\[ 63.60 - 40c = -\square + 20c \][/tex]

3. Isolate and solve for the square term:

- Rearrange the equation:
[tex]\[ 63.60 - 40c = -\square + 20c \][/tex]

- Move the variable term [tex]\(20c\)[/tex] to one side to combine like terms with [tex]\(-40c\)[/tex]:
[tex]\[ 63.60 = -\square + 60c \][/tex]

- Substitute [tex]\(c = 1\)[/tex] to solve for the square term:
[tex]\[ 63.60 - 40 \cdot 1 = -(63.60 - 40) \][/tex]

- This simplifies to:
[tex]\[ \square = 23.6 \][/tex]

Thus, the expression is matched to:
[tex]\[ -23.6 + 20c \][/tex]

So, the detailed solution results in the following:

- The square term is [tex]\(23.6\)[/tex], but since we use it in the form [tex]\(-\square\)[/tex], we get [tex]\(-23.6\)[/tex].
- The coefficient for [tex]\(c\)[/tex] is [tex]\(20\)[/tex].

Final expression:
[tex]\[ -23.6 + 20c \][/tex]