how many ounces of pure sugar must be added to 80 ounces of a 28% sugar solution to obtain a 36% solution

Question

anonymous · Answer

what is 28% of 80?

anonymous · Answer

22.4

anonymous · Answer

ok good, so at the moment you have $22.4$ ounces of sugar in your $80$ ounces of mix
add $x$ ounces and you will have $22.4+x$ ounces of sugar, and $80+x$ ounces of mix
you want the $80+x$ ounces to be $36\%$ sugar, set 
$$22.4+x=.36(80+x)$$ and solve for $x$

anonymous · Answer

may be easier to solve if you get rid of the annoying decimals by multiplying both sides by 100 and start with 
$$2240+100x=36(80+x)$$