400÷х=1000÷10

To solve the equation \( \frac{400}{x} = \frac{1000}{10} \), we first simplify the right side:

\[ \frac{1000}{10} = 100 \]

Now, we rewrite the equation:

\[ \frac{400}{x} = 100 \]

Next, we can cross-multiply:

\[ 400 = 100x \]

Now, divide both sides by 100 to solve for \( x \):

\[ x = \frac{400}{100} = 4 \]

Thus, the solution is:

\[ x = 4 \]