Try this:
1) note that weight of pure antifreeze before mixing and after mixing is the same. So, if 'x' is weight of pure antifreeze in 50% solution, it is possible to make up equation before mixing: 0.5x+0.2*90.
2) there are 0.2*90=18 gal. of pure antifreeze in the 20% solution. If 'x' gal. is the weight of pure antifreeze in 50% sol. and 18 gal. is the weight of pure antifreeze in 20% sol., it is possible to make up an equation after mixing: 0.4(x+18).
3) using the both parts: 0.5x+0.2*90=0.4(x+18) ⇒ x=54 gal. of <u>pure</u> weight.
4) to find 50% solution of 54 gal. pure weight just 54:0.5=108 gal.
Answer: 108 gal.
3/15 means if you pay the bill within 15 you will get a discount by 3%
Now solve your question
178.95−(178.95×0.03)
=173.58 be paid
You can use the formula x2-x1 over y2-y1
Hey!
Here is the equation:

Switch the equation around and it becomes:

The sign changes when moved to the other sign. At first it was (÷) and now it's (×).
Multiply 4.5 by 3 to find j

<em>That means your answer is 13.5</em>

Work is attached in the image provided.