You are going to mix a gallon bucket of window cleaner. The instructions direct you to mix 1 part cleaner to 3 parts water. How much cleaning solution will you need to use?
A) 1 ½ quarts B)1 pint C) 2 quarts D) 1 quart

One gallon equals to 4 quarts.

The instructions tell you to add 1 part of cleaner and 3 parts of water, in total 4 parts. It makes it easy as you can take that one part = one quart.

You will use 3 quarts of water and 1 quart of cleaner. The answer is D.

Let
x-> gallons of cleaner
y-> gallons of water

we know that
$$x+y=1$$ equation 1
and
$$\frac{x}{y} = \frac{1}{3} \\ y=3x$$ equation 2
substitute equation 2 in equation 1
$$x+3x=1 \\ 4x=1 \\ x=1/4 gal$$

find the value of y
$$y=3x \\ y=3* \frac{1}{4} \\ y= \frac{3}{4} gal$$

we know that
$$\frac{1}{4} gal$$ is equal to $$1 quart$$

therefore