Question 542611
<pre><font size = 4><b>
<font color = "red">-13a</font><font color = "indigo">+6</font><font color = "green">-4c</font><font color = "indigo">-11</font><font color = "red">+5a</font><font color = "green">-2c</font>

Combine the <font color = "red">red</font> terms. They are like terms because they both have
<font color = "red">a</font>'s:    <font color = "red">-13a+5a = -8a</font>.

Combine the <font color = "indigo">purple</font> terms. They are like terms because they both are just 
plain numbers with no letter:    <font color = "indigo">+6-11 = -5</font>.

Combine the <font color = "green">green</font> terms. They are like terms because they both have 
<font color = "green">c</font>'s:    <font color = "green">-4c-2c = -6c</font>.
 
Final answer:  

<font color = "red">-8a</font><font color = "indigo">-5</font><font color = "green">-6c</font>.

Edwin</pre>