(21•15):x=68•5

To solve the equation \((21 \cdot 15) : x = 68 \cdot 5\), we can start by calculating the left and right sides of the equation.

1. Calculate \(21 \cdot 15\): \[ 21 \cdot 15 = 315 \]

2. Calculate \(68 \cdot 5\): \[ 68 \cdot 5 = 340 \]

Now, substitute these results back into the equation:

\[ \frac{315}{x} = 340 \]

Next, we can cross-multiply to solve for \(x\):

\[ 315 = 340x \]

Now divide both sides by \(340\):

\[ x = \frac{315}{340} \]

To simplify this fraction, we can divide the numerator and the denominator by their greatest common divisor, which is 5:

\[ x = \frac{63}{68} \]

Thus, the solution for \(x\) is:

\[ x = \frac{63}{68} \]