A 120 watt light-bulb is a 0.120 kilowatt light bulb.
In one hour, it uses 0.120 kilowatt-hour of energy.
If electrical energy costs $0.20 per kilowatt hour, then that light bulb costs
(0.120 kilowatt-hour / hour) x (0.20 dollar / kilowatt-hour) =
(0.120 x $0.20 / hour) =
$0.024 / hour = <span>2.4¢ per hour </span>
Answer: x = -0.2651 and y = -0.9759
Step-by-step explanation:
Solution by substitution method
8x+5y= -7
-7x+6y= -4 = 7x-6y=4
Suppose,
8x+5y=-7→(1)
7x-6y=4→(2)
Taking equation (1), we have
8x+5y= -7
⇒8x= -5y -7
⇒x= -5y-7 / 8 →(3)
Putting x= -5y-7 / 8
in equation (2), we get 7x-6y=4
7(-5y-7/8)-6y=4
⇒-35y-49-48y=32
⇒-83y-49=32
⇒-83y=32+49
⇒-83y=81
⇒y= 81 / -83
⇒y= -0.9759→(4)
Now, Putting y= -0.9759 in equation (3), we get
x= -5y-7
x= -5(-0.9759)-7/8
⇒x= 4.8795-7/8
⇒x= -2.1205/8
⇒x= -0.2651
∴x= -0.2651 and y = -0.9759
