A way to make a approximation to a given number by using fewer digits is called <u>rounding</u>
<em>How you round:</em>
<em>If the next smallest place value is greater than or equal to five (5, 6, 7, 8, or 9), you increase the value of the digit you're rounding to by one (+1). Any remaining digits before the decimal point become zeros, and any that are after the decimal point are dropped. </em>
The variable a minus 10 equals 6. If you substituted a for 16, and subtracted 10, you'd get 6. Substituting the rest of the numbers and subtracting 10 wouldn't give you 6.
