Answer:
Here we want to calculate the 25% of $140.
Well, first we assume that:
$140 = 100%.
Now, assuming that, we can write the equation:
X = 25%
Where X is the 25% of $140.
Then we have the equations:
$140 = 100%
X = 25%
Let's take the quotient between these equations:
$140/X = (100%/25%)
Now let's solve this for X:
X = (25%/100%)*$140 = 0.25*$140 = $35
Then the tip will be of $35