`78.5% of 640 + 36% of 785 - ? = 21 xx 29`, find ?

Options

A. 173
B. 143
C. 151
D. 176

Answer

To solve the equation \( 78.5\% \text{ of } 640 + 36\% \text{ of } 785 - ? = 21 \times 29 \), we will follow these steps:

### Step 1: Calculate \( 21 \times 29 \)
First, we need to calculate the right-hand side of the equation.

\[ 21 \times 29 = 609 \]

### Step 2: Calculate \( 78.5\% \text{ of } 640 \)
Next, we calculate \( 78.5\% \text{ of } 640 \).

\[ 78.5\% = \frac{78.5}{100} = 0.785 \]
\[ 0.785 \times 640 = 502.4 \]

### Step 3: Calculate \( 36\% \text{ of } 785 \)
Now, we calculate \( 36\% \text{ of } 785 \).

\[ 36\% = \frac{36}{100} = 0.36 \]
\[ 0.36 \times 785 = 282.6 \]

### Step 4: Combine the results from Steps 2 and 3
Now, we add the results from Steps 2 and 3.

\[ 502.4 + 282.6 = 785 \]

### Step 5: Set up the equation
We can now set up the equation based on our calculations:

\[ 785 - ? = 609 \]

### Step 6: Solve for \( ? \)
To find \( ? \), we rearrange the equation:

\[ ? = 785 - 609 \]
\[ ? = 176 \]

### Final Answer
Thus, the value of \( ? \) is \( 176 \).

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