Let's solve each of the given expressions step by step:

### a. \(-75 + 32 - 5\)

1. Start with \(-75\).
2. Add \(32\): \(-75 + 32 = -43\).
3. Subtract \(5\): \(-43 - 5 = -48\).

So, \(a = -48\).

### b. \(-20.7 - 40\)

1. Start with \(-20.7\).
2. Subtract \(40\): \(-20.7 - 40 = -60.7\).

So, \(b = -60.7\).

### c. \(200 : (-2) + 180\)

1. Divide \(200\) by \(-2\): \(200 / (-2) = -100\).
2. Add \(180\): \(-100 + 180 = 80\).

So, \(c = 80\).

### d. \((5x - 3) + (1 - 2y) mũ6 = 0\)

It seems like there might be a typo or misunderstanding in the expression, particularly with "mũ6". Assuming "mũ6" means raising to the power of 6, the expression could be interpreted as:

\[
(5x - 3) + (1 - 2y)^6 = 0
\]

To solve for \(x\) and \(y\), we need more information, such as specific values or additional equations. If we are to solve for \(x\) and \(y\) in terms of each other, we can isolate one variable:

\[
(5x - 3) + (1 - 2y)^6 = 0
\]

Rearrange to solve for \(5x - 3\):

\[
5x - 3 = -(1 - 2y)^6
\]

Then solve for \(x\):

\[
5x = -(1 - 2y)^6 + 3
\]

\[
x = \frac{-(1 - 2y)^6 + 3}{5}
\]

So, \(x\) is expressed in terms of \(y\):

\[
x = \frac{3 - (1 - 2y)^6}{5}
\]

Without additional context or constraints, this is the simplified form of the equation.