Online Course Discussion Forum

Math Challenge I-C Algebra 2.14

 
 
Picture of Han Li
Math Challenge I-C Algebra 2.14
by Han Li - Sunday, 24 September 2023, 1:58 PM
 

I don't understand why the answer for 2.14 is B. Could someone please explain why?

 
Picture of Dr. Kevin Wang
Re: Math Challenge I-C Algebra 2.14
by Dr. Kevin Wang - Sunday, 24 September 2023, 2:42 PM
 

The question wants $x < 7$ and $x < 13$.  Between these two requirements, $x < 7$ is more restrictive.  In other words, for all $x$ values that are less than $7$, they are already also less than $13$.  Therefore the requirement that $x < 7$ already covers $x < 13$, and the two requirements can be combined into just $x < 7$.  So the answer is $B$, $(-\infty, 7)$.