Hello! The first thing to do is to find the amount of change by subtracting both numbers. 2.60 - 0.25 is 2.35. Now, we set up a proportion by doing change/original = x/100. With the values plugged in, it would be written like this: 2.35/0.25 = x/100. Cross multiply the values in the proportion. When you do, you get 235 = 0.25x. Now, divide each side by 0.25 to isolate the "x". When you do that, x = 940. The price of gas has gone up 940% since 1930.
12.60 / 7 = $ 1.80 per bottle
10.98 / 6 = $ 1.83 per bottle
18.10 / 10 = $ 1.81 per bottle
16.38 / 9 = $ 1.82 per bottle
best buy (cheapest) is : $ 12.60 for 7 bottles <==
So first, you have to get two of the same variables to cancel out. Let's do this for x. In order for the x's to cancel out, we could multiply the bottom problem by 2.
(2) 3x-6y=24
After multiplying all the numbers by 2, you get the equation 6x-12y=48
The set of equations is now
-6x+2y=12
6x-12y=48
Now you can add them. The x variables cancel out, so you are left with the y variable.
2y+-12y=-10y and 12+48=60
Then you would divide 60 by -10 to get y=-6.
You would plug the answer for y into one of the original equations, lets do the top one. -6x+2y=12 becomes -6x+2(-6)=12
You'd multiply the 2 and -6 to get -12 so the equation is
-6x-12=12
The negative 12 turn positive and you add to both sides to get the -6x alone.
-6x-12=12
+12=12
-6x=24
Then divide 24 by -6
X=4
(-4,-6) is your final answer.
