Joan sold half of her comic books and then bought 8 more. She now has 15. How many did she begin with?

Question

8097 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-11-01T14:11:42

#14#

Let's construct an equation for the question and solve it

Let the number of comic books that Joan had in the beginning is #x#

In the start she sold half her books (so,multiply by #1/2#)

#color(red)(x*1/2#

Next, she bought #8# more books (so,add #8#)

#color(red)(x*1/2+8#

At the last she has #15# books (so,let the equation equal #15#)

#color(red)(x*1/2+8=15#

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Now let's solve the completed equation

#rarrx*1/2+8=15#

Subtract #8# both sides

#rarrx*1/2+cancel8-cancelcolor(violet)(8)=15-color(violet)(8)#

#rarrx*1/2=7#

Multiply both sides by #2#

#rarrx*1/cancel2*cancelcolor(violet)(2)=7*color(violet)(2)#

#color(green)(rArrx=14#

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So Joan started with #14# comic books

Hope this helps !...

:)