We've seen how to substitute numerical values for pronumerals before. We follow the same process when the numerical values are negative.
Evaluate $7x5$7x−5 when $x=6$x=6 and also when $x=6$x=−6.
Think: There are two different values of $x$x, so we should substitute and then evaluate them individually.
Do: Let's substitute $x=6$x=6 first.
$7x5$7x−5  $=$=  $7\times65$7×6−5 
Substitute $x=6$x=6. 
$=$=  $425$42−5 
Evaluate the multiplication 

$=$=  $37$37 
Evaluate the subtraction 
Now let's substitute $x=6$x=−6.
$7x5$7x−5  $=$=  $7\times\left(6\right)5$7×(−6)−5 
Substitute $x=6$x=−6. 
$=$=  $425$−42−5 
Evaluate the multiplication 

$=$=  $47$−47 
Evaluate the subtraction 
Reflect: Notice that the values of $x$x are the negatives of each other, but the values of the expression are not. It is important that when we substitute values, the value that we substitute fits into exactly the same position as the pronumeral, and that we follow the order of operations.
Find the value of $m+n$m+n when $m=6$m=6 and $n=4$n=−4.
Find the value of $\frac{p}{2q}$p2q when $p=28$p=−28 and $q=7$q=−7.
Find the value of $k^2$k2 when $k=7$k=−7.
operates with positiveinteger and zero indices of numerical bases