To solve this, you must find a common denominator (the number on the bottom of the fraction) before adding the numbers. The easiest was to do this is multiply the denominators together to get a common product. You then multiply by that number over itself, because that is equivalent to 1. So in this problem, you would multiply 3/4 by 19/19 and 18/19 by 4/4. Once you do this, you can add the fractions together.
Use substitution and substitute y into the other equation. One of the equations already gives you y in terms of x, so use that and substitute it into the other equation. y = 3x - 4
Plug into the other equation: -3y = -9x + 12
-3(3x-4) = -9x + 12
-9x + 12 = -9x + 12
This is an identity. So that means that any value of x makes this equation true. So B.
21) 473 1/5
22) 1/3
23) 4 1/4
Answer: 55/72
Step-by-step explanation:
$370.80 is the right answer