If you compare the two fractions, you can see that you need to multiply by #5# on the top to get from the left one to the right one:
#2/5 stackrel(stackrel(xx5=)color(red)rarr) color(white)overbrace(quadcolor(black)=quad) 10/(x+5)#
This means that you will also need to multiply by #5# on the bottom to keep it the same.
#2/5 color(white)underbrace(quadcolor(black)=quad)_(stackrel(xx5=)color(red)rarr)10/(x+5)#
(Please excuse the formatting, I couldn't get it to looks like the top one.)
The top equation is #2xx5=10#, and the bottom equation will now be #5xx5=x+5#, which we can now solve for #x#:
#5xx5=x+5#
#25=x+5#
#25color(blue)-color(blue)5=x+5color(blue)-color(blue)5#
#25color(blue)-color(blue)5=xcolor(red)cancelcolor(black)(color(black)+5color(blue)-color(blue)5)#
#25color(blue)-color(blue)5=x#
#20=x#
#x=20#
That's the answer. Hope this helped!
