Step 1: Our output value is 350.
Step 2: We represent the unknown value with $x$.
Step 3: From step 1 above,$350=100\%$.
Step 4: Similarly, $x=25\%$.
Step 5: This results in a pair of simple equations:
$350=100\%(1)$.
$x=25\%(2)$.
Step 6: By dividing equation 1 by equation 2 and noting that both the RHS (right hand side) of both
equations have the same unit (%); we have
$\frac{350}{x}=\frac{100\%}{25\%}$
Step 7: Again, the reciprocal of both sides gives
$\frac{x}{350}=\frac{25}{100}$
$\⇒x=87.5$
Therefore, $25\%$ of $350$ is $87.5$