<PRE><B>Question 1198862</B>
&lt;br&gt;
Use the two given numbers in the sequence to find the common difference.&lt;br&gt;
a5 is equal to a1 plus the common difference 5-1=4 times:&lt;br&gt;
-17 = 3 + 4d
-20 = 4d
d = -5&lt;br&gt;
Use that common difference and one of the given numbers to find the 21st term.&lt;br&gt;
a21 is equal to a1 plus the common difference 21-1=20 times:&lt;br&gt;
a21 = 3+20(-5) = 3-100 = -97&lt;br&gt;
</PRE>