A 40% dye solution is to be mixed with a 70% dye solution to get 120% liters of a 50% dye solution. How many liters of the 40% and 70% solutions will be needed?? NEED HELP

Question

anonymous · Answer

we need a variable, say $x$ is the number of liters of 70% solution
then since the total is $120$ liters, the amount of 40% solution must be $120-x$

anonymous · Answer

the $x$ liters of 70% solution has $.7x$ dye, and the $120-x$ liters of 40% solution has $.4(120-x)$ dye
you want the total to be 50% of 120, which is half of 120, which is 60
solve 
$$.7x+.4(120-x)=60$$ for $x$

anonymous · Answer

probably easier to get rid of annoying decimal by multiplying both sides by 10 and solve 
$$7x+4(120-x)=600$$ in just a few steps

anonymous · Answer

you good from there?

anonymous · Answer

where did you get the 600 from??

anonymous · Answer

@satellite73