So for this problem, we will be using the exponential equation format, which is y = ab^x. The a variable is the initial value, and the b variable is the growth/decay.
Since our touchscreen starts off at a value of 1200, that will be our a variable.
Since the touchscreen is decaying in value by 25%, subtract 0.25 (25% in decimal form) from 1 to get 0.75. 0.75 is going to be your b variable.
In this case, time is our independent variable. Since we want to know the value 3 years from now, 3 is the x variable.
Using our info above, we can solve for y, which is the cost after x years.

In context, after 3 years the touchscreen will only be worth $506.
Your answer is -5.
This is because, if you expand the single bracket, you get -6x -3a, and since the other side of the equals sign is -6x + 15, then you need to do 15 ÷ -3 = -5.
I hope this helps!
5x - 3y = 15
5x - <u>5x</u> -3y = <u>- 5x</u> + 15
<u>-3y</u> = <u>-5x</u> + 15
3y = 5x - 15
divide all of them by 3...
y = 5/3 - 5
Answer:
5.5
Step-by-step explanation: