To solve the equation \( 20 = 5 - \frac{3}{8} x \), we will start by isolating \( x \).
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First, subtract 5 from both sides: \[ 20 - 5 = -\frac{3}{8} x \] \[ 15 = -\frac{3}{8} x \]
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Next, we want to get rid of the negative coefficient on \( x \) by multiplying both sides by -1: \[ -15 = \frac{3}{8} x \]
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Now, to solve for \( x \), multiply both sides by the reciprocal of \( \frac{3}{8} \), which is \( \frac{8}{3} \): \[ x = -15 \cdot \frac{8}{3} \]
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Calculate the right side: \[ x = -\frac{15 \cdot 8}{3} = -\frac{120}{3} = -40 \]
Thus, the solution is: \[ x = -40 \]